コード例 #1
0
    def model_fn(features, labels, mode, params):  # pylint: disable=unused-argument
        """The `model_fn` for TPUEstimator."""

        tf.logging.info("*** Features ***")
        for name in sorted(features.keys()):
            tf.logging.info("  name = %s, shape = %s" %
                            (name, features[name].shape))

        input_ids = features["input_ids"]
        input_mask = features["input_mask"]
        segment_ids = features["segment_ids"]
        label_ids = features["label_ids"]
        is_real_example = None
        if "is_real_example" in features:
            is_real_example = tf.cast(features["is_real_example"],
                                      dtype=tf.float32)
        else:
            is_real_example = tf.ones(tf.shape(label_ids), dtype=tf.float32)

        is_training = (mode == tf.estimator.ModeKeys.TRAIN)

        (total_loss, per_example_loss, logits,
         probabilities) = create_model(bert_config, is_training, input_ids,
                                       input_mask, segment_ids, label_ids,
                                       num_labels, use_one_hot_embeddings)

        tvars = tf.trainable_variables()
        initialized_variable_names = {}
        scaffold_fn = None
        if init_checkpoint:
            (assignment_map, initialized_variable_names
             ) = modeling.get_assignment_map_from_checkpoint(
                 tvars, init_checkpoint)
            if use_tpu:

                def tpu_scaffold():
                    tf.train.init_from_checkpoint(init_checkpoint,
                                                  assignment_map)
                    return tf.train.Scaffold()

                scaffold_fn = tpu_scaffold
            else:
                tf.train.init_from_checkpoint(init_checkpoint, assignment_map)

        tf.logging.info("**** Trainable Variables ****")
        for var in tvars:
            init_string = ""
            if var.name in initialized_variable_names:
                init_string = ", *INIT_FROM_CKPT*"
            tf.logging.info("  name = %s, shape = %s%s", var.name, var.shape,
                            init_string)

        output_spec = None
        if mode == tf.estimator.ModeKeys.TRAIN:

            train_op = optimization_hvd.create_optimizer(
                total_loss, learning_rate, num_train_steps, num_warmup_steps,
                use_tpu)

            output_spec = tf.contrib.tpu.TPUEstimatorSpec(
                mode=mode,
                loss=total_loss,
                train_op=train_op,
                scaffold_fn=scaffold_fn)
        elif mode == tf.estimator.ModeKeys.EVAL:

            def metric_fn(per_example_loss, label_ids, logits,
                          is_real_example):
                predictions = tf.argmax(logits, axis=-1, output_type=tf.int32)
                accuracy = tf.metrics.accuracy(labels=label_ids,
                                               predictions=predictions,
                                               weights=is_real_example)
                loss = tf.metrics.mean(values=per_example_loss,
                                       weights=is_real_example)
                return {
                    "eval_accuracy": accuracy,
                    "eval_loss": loss,
                }

            eval_metrics = (metric_fn, [
                per_example_loss, label_ids, logits, is_real_example
            ])
            output_spec = tf.contrib.tpu.TPUEstimatorSpec(
                mode=mode,
                loss=total_loss,
                eval_metrics=eval_metrics,
                scaffold_fn=scaffold_fn)
        else:
            output_spec = tf.contrib.tpu.TPUEstimatorSpec(
                mode=mode,
                predictions={"probabilities": probabilities},
                scaffold_fn=scaffold_fn)
        return output_spec
コード例 #2
0
    def model_fn(features, labels, mode, params):  # pylint: disable=unused-argument
        """The `model_fn` for TPUEstimator."""

        tf.logging.info("*** Features ***")
        for name in sorted(features.keys()):
            tf.logging.info("  name = %s, shape = %s" %
                            (name, features[name].shape))

        input_ids = features["input_ids"]
        input_mask = features["input_mask"]
        segment_ids = features["segment_ids"]
        masked_lm_positions = features["masked_lm_positions"]
        masked_lm_ids = features["masked_lm_ids"]
        masked_lm_weights = features["masked_lm_weights"]
        next_sentence_labels = features["next_sentence_labels"]

        is_training = (mode == tf.estimator.ModeKeys.TRAIN)

        model = modeling.BertModel(
            config=bert_config,
            is_training=is_training,
            input_ids=input_ids,
            input_mask=input_mask,
            token_type_ids=segment_ids,
            use_one_hot_embeddings=use_one_hot_embeddings)

        (masked_lm_loss, masked_lm_example_loss,
         masked_lm_log_probs) = get_masked_lm_output(
             bert_config, model.get_sequence_output(),
             model.get_embedding_table(), masked_lm_positions, masked_lm_ids,
             masked_lm_weights)

        (next_sentence_loss, next_sentence_example_loss,
         next_sentence_log_probs) = get_next_sentence_output(
             bert_config, model.get_pooled_output(), next_sentence_labels)

        total_loss = masked_lm_loss + next_sentence_loss

        tvars = tf.trainable_variables()

        initialized_variable_names = {}
        scaffold_fn = None
        if init_checkpoint:
            (assignment_map, initialized_variable_names
             ) = modeling.get_assignment_map_from_checkpoint(
                 tvars, init_checkpoint)
            if use_tpu:

                def tpu_scaffold():
                    tf.train.init_from_checkpoint(init_checkpoint,
                                                  assignment_map)
                    return tf.train.Scaffold()

                scaffold_fn = tpu_scaffold
            else:
                tf.train.init_from_checkpoint(init_checkpoint, assignment_map)

        tf.logging.info("**** Trainable Variables ****")
        for var in tvars:
            init_string = ""
            if var.name in initialized_variable_names:
                init_string = ", *INIT_FROM_CKPT*"
            tf.logging.info("  name = %s, shape = %s%s", var.name, var.shape,
                            init_string)

        output_spec = None
        if mode == tf.estimator.ModeKeys.TRAIN:
            train_op = optimization_hvd.create_optimizer(
                total_loss, learning_rate, num_train_steps, num_warmup_steps,
                use_tpu, freeze)

            if freeze:
                tf.logging.info("**** Freeze Layers ****")

            output_spec = tf.contrib.tpu.TPUEstimatorSpec(
                mode=mode,
                loss=total_loss,
                train_op=train_op,
                scaffold_fn=scaffold_fn)
        elif mode == tf.estimator.ModeKeys.EVAL:

            def metric_fn(masked_lm_example_loss, masked_lm_log_probs,
                          masked_lm_ids, masked_lm_weights,
                          next_sentence_example_loss, next_sentence_log_probs,
                          next_sentence_labels):
                """Computes the loss and accuracy of the model."""
                masked_lm_log_probs = tf.reshape(
                    masked_lm_log_probs, [-1, masked_lm_log_probs.shape[-1]])
                masked_lm_predictions = tf.argmax(masked_lm_log_probs,
                                                  axis=-1,
                                                  output_type=tf.int32)
                masked_lm_example_loss = tf.reshape(masked_lm_example_loss,
                                                    [-1])
                masked_lm_ids = tf.reshape(masked_lm_ids, [-1])
                masked_lm_weights = tf.reshape(masked_lm_weights, [-1])
                masked_lm_accuracy = tf.metrics.accuracy(
                    labels=masked_lm_ids,
                    predictions=masked_lm_predictions,
                    weights=masked_lm_weights)
                masked_lm_mean_loss = tf.metrics.mean(
                    values=masked_lm_example_loss, weights=masked_lm_weights)

                next_sentence_log_probs = tf.reshape(
                    next_sentence_log_probs,
                    [-1, next_sentence_log_probs.shape[-1]])
                next_sentence_predictions = tf.argmax(next_sentence_log_probs,
                                                      axis=-1,
                                                      output_type=tf.int32)
                next_sentence_labels = tf.reshape(next_sentence_labels, [-1])
                next_sentence_accuracy = tf.metrics.accuracy(
                    labels=next_sentence_labels,
                    predictions=next_sentence_predictions)
                next_sentence_mean_loss = tf.metrics.mean(
                    values=next_sentence_example_loss)

                return {
                    "masked_lm_accuracy": masked_lm_accuracy,
                    "masked_lm_loss": masked_lm_mean_loss,
                    "next_sentence_accuracy": next_sentence_accuracy,
                    "next_sentence_loss": next_sentence_mean_loss,
                }

            eval_metrics = (metric_fn, [
                masked_lm_example_loss, masked_lm_log_probs, masked_lm_ids,
                masked_lm_weights, next_sentence_example_loss,
                next_sentence_log_probs, next_sentence_labels
            ])
            output_spec = tf.contrib.tpu.TPUEstimatorSpec(
                mode=mode,
                loss=total_loss,
                eval_metrics=eval_metrics,
                scaffold_fn=scaffold_fn)
        else:
            raise ValueError("Only TRAIN and EVAL modes are supported: %s" %
                             (mode))

        return output_spec
コード例 #3
0
  def model_fn(features, labels, mode, params):  # pylint: disable=unused-argument
    """The `model_fn` for TPUEstimator."""

    tf.logging.info("*** Features ***")
    for name in sorted(features.keys()):
      tf.logging.info("  name = %s, shape = %s" % (name, features[name].shape))

    unique_ids = features["unique_ids"]
    input_ids = features["input_ids"]
    input_mask = features["input_mask"]
    segment_ids = features["segment_ids"]

    is_training = (mode == tf.estimator.ModeKeys.TRAIN)

    (start_logits, end_logits) = create_model(
        bert_config=bert_config,
        is_training=is_training,
        input_ids=input_ids,
        input_mask=input_mask,
        segment_ids=segment_ids,
        use_one_hot_embeddings=use_one_hot_embeddings)

    tvars = tf.trainable_variables()

    initialized_variable_names = {}
    scaffold_fn = None
    if init_checkpoint:
      (assignment_map, initialized_variable_names
      ) = modeling.get_assignment_map_from_checkpoint(tvars, init_checkpoint)
      if use_tpu:

        def tpu_scaffold():
          tf.train.init_from_checkpoint(init_checkpoint, assignment_map)
          return tf.train.Scaffold()

        scaffold_fn = tpu_scaffold
      else:
        tf.train.init_from_checkpoint(init_checkpoint, assignment_map)

    tf.logging.info("**** Trainable Variables ****")
    for var in tvars:
      init_string = ""
      if var.name in initialized_variable_names:
        init_string = ", *INIT_FROM_CKPT*"
      tf.logging.info("  name = %s, shape = %s%s", var.name, var.shape,
                      init_string)

    output_spec = None
    if mode == tf.estimator.ModeKeys.TRAIN:
      seq_length = modeling.get_shape_list(input_ids)[1]

      def compute_loss(logits, positions):
        one_hot_positions = tf.one_hot(
            positions, depth=seq_length, dtype=tf.float32)
        log_probs = tf.nn.log_softmax(logits, axis=-1)
        loss = -tf.reduce_mean(
            tf.reduce_sum(one_hot_positions * log_probs, axis=-1))
        return loss

      start_positions = features["start_positions"]
      end_positions = features["end_positions"]

      start_loss = compute_loss(start_logits, start_positions)
      end_loss = compute_loss(end_logits, end_positions)

      total_loss = (start_loss + end_loss) / 2.0

      train_op = optimization_hvd.create_optimizer(
          total_loss, learning_rate, num_train_steps, num_warmup_steps, use_tpu)

      output_spec = tf.contrib.tpu.TPUEstimatorSpec(
          mode=mode,
          loss=total_loss,
          train_op=train_op,
          scaffold_fn=scaffold_fn)
    elif mode == tf.estimator.ModeKeys.PREDICT:
      predictions = {
          "unique_ids": unique_ids,
          "start_logits": start_logits,
          "end_logits": end_logits,
      }
      output_spec = tf.contrib.tpu.TPUEstimatorSpec(
          mode=mode, predictions=predictions, scaffold_fn=scaffold_fn)
    else:
      raise ValueError(
          "Only TRAIN and PREDICT modes are supported: %s" % (mode))

    return output_spec
コード例 #4
0
  def model_fn(features, labels, mode, params):  # pylint: disable=unused-argument
    """The `model_fn` for TPUEstimator."""

    tf.logging.info("*** Features ***")
    for name in sorted(features.keys()):
      tf.logging.info("  name = %s, shape = %s" % (name, features[name].shape))

    input_ids = features["input_ids"]
    input_mask = features["input_mask"]
    segment_ids = features["segment_ids"]
    label_ids = features["label_ids"]
    is_real_example = None
    if "is_real_example" in features:
      is_real_example = tf.cast(features["is_real_example"], dtype=tf.float32)
    else:
      is_real_example = tf.ones(tf.shape(label_ids), dtype=tf.float32)

    is_training = (mode == tf.estimator.ModeKeys.TRAIN)

    (total_loss, per_example_loss, logits, probabilities) = create_model(
        bert_config, is_training, input_ids, input_mask, segment_ids, label_ids,
        num_labels, use_one_hot_embeddings)
    
    ##******************************************************
    predictions = tf.argmax(logits, axis=-1, output_type=tf.int32)
    one_hot_labels = tf.one_hot(label_ids, depth=num_labels, dtype=tf.float32)
    
    
    tf.logging.info("**** label_ids **** is: %s", label_ids) #shape=(32,)
    tf.logging.info("**** logits **** is: %s", logits) #shape=(32, 2)
    tf.logging.info("**** probabilities **** is: %s", probabilities) #shape=(32, 2)
    tf.logging.info("**** predictions **** is: %s", predictions) #shape=(32,)
    tf.logging.info("**** one_hot_labels **** is: %s", one_hot_labels) #shape=(32, 2)
    
    ## add loss to tensorboard (ok)
    tf.summary.scalar('total_loss', total_loss)
    
    # add cross_entropy to tensorboard (ok)
    with tf.variable_scope('cross_entropy'):
      diff = tf.nn.softmax_cross_entropy_with_logits(labels=one_hot_labels, logits=logits)
      cross_entropy = tf.reduce_mean(diff)
    tf.summary.scalar('cross_entropy', cross_entropy)
    '''
    # add learning_rate to tensorboard (ok)
    #with tf.name_scope('learning_rate'):
    #  train_step = tf.train.AdamOptimizer(FLAGS.learning_rate).minimize(cross_entropy)
    #tf.summary.scalar('learning_rate', learning_rate)
    '''
    # add accuracy to tensorboard (ok)
    with tf.name_scope('accuracy'):
      #accuracy = tf.metrics.accuracy(label_ids, predictions)
      correct_prediction = tf.equal(tf.argmax(one_hot_labels, axis=1), tf.argmax(logits, axis=1))
      accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))
      tf.summary.scalar('accuracy', accuracy)
    
    #merged = tf.summary.merge_all()
    #train_writer = tf.summary.FileWriter(FLAGS.log_dir + '/train', sess.graph)
    
    ##******************************************************
    
    tvars = tf.trainable_variables()
    initialized_variable_names = {}
    scaffold_fn = None
    if init_checkpoint:
      (assignment_map, initialized_variable_names
      ) = modeling.get_assignment_map_from_checkpoint(tvars, init_checkpoint)
      if use_tpu:

        def tpu_scaffold():
          tf.train.init_from_checkpoint(init_checkpoint, assignment_map)
          return tf.train.Scaffold()

        scaffold_fn = tpu_scaffold
      else:
        tf.train.init_from_checkpoint(init_checkpoint, assignment_map)

    tf.logging.info("**** Trainable Variables ****")
    for var in tvars:
      init_string = ""
      if var.name in initialized_variable_names:
        init_string = ", *INIT_FROM_CKPT*"
      tf.logging.info("  name = %s, shape = %s%s", var.name, var.shape,
                      init_string)

    output_spec = None
    if mode == tf.estimator.ModeKeys.TRAIN:

      train_op = optimization_hvd.create_optimizer(
          total_loss, learning_rate, num_train_steps, num_warmup_steps, use_tpu)

      output_spec = tf.contrib.tpu.TPUEstimatorSpec(
          mode=mode,
          loss=total_loss,
          train_op=train_op,
          scaffold_fn=scaffold_fn)
    elif mode == tf.estimator.ModeKeys.EVAL:

      def metric_fn(per_example_loss, label_ids, logits, is_real_example):
        predictions = tf.argmax(logits, axis=-1, output_type=tf.int32)
        accuracy = tf.metrics.accuracy(
            labels=label_ids, predictions=predictions, weights=is_real_example)
        loss = tf.metrics.mean(values=per_example_loss, weights=is_real_example)
        return {
            "eval_accuracy": accuracy,
            "eval_loss": loss,
        }

      eval_metrics = (metric_fn,
                      [per_example_loss, label_ids, logits, is_real_example])
      output_spec = tf.contrib.tpu.TPUEstimatorSpec(
          mode=mode,
          loss=total_loss,
          eval_metrics=eval_metrics,
          scaffold_fn=scaffold_fn)
    else:
      '''
      output_spec = tf.contrib.tpu.TPUEstimatorSpec(
          mode=mode,
          predictions={"probabilities": probabilities},
          scaffold_fn=scaffold_fn)
      '''
      predictions = tf.argmax(probabilities, axis=-1, output_type=tf.int32) #logits-->probabilities
      export_outputs={'classes': tf.estimator.export.PredictOutput(
                            {"probabilities": probabilities, "classid": predictions})}
      output_spec = tf.contrib.tpu.TPUEstimatorSpec(
          mode=mode, predictions=probabilities, scaffold_fn=scaffold_fn, export_outputs=export_outputs)
        
    return output_spec
コード例 #5
0
    def model_fn(features, labels, mode, params):  # pylint: disable=unused-argument
        """The `model_fn` for TPUEstimator."""

        tf.logging.info("*** Features ***")
        for name in sorted(features.keys()):
            tf.logging.info("  name = %s, shape = %s" %
                            (name, features[name].shape))

        input_ids = features["input_ids"]
        input_mask = features["input_mask"]
        segment_ids = features["segment_ids"]
        masked_lm_positions = features["masked_lm_positions"]
        masked_lm_ids = features["masked_lm_ids"]
        masked_lm_weights = features["masked_lm_weights"]
        next_sentence_labels = features["next_sentence_labels"]

        is_training = (mode == tf.estimator.ModeKeys.TRAIN
                       )  # where assigns mode?

        model = modeling.BertModel(
            config=bert_config,
            is_training=is_training,
            input_ids=input_ids,
            input_mask=input_mask,
            token_type_ids=segment_ids,
            use_one_hot_embeddings=use_one_hot_embeddings,
            add_weight=add_weight,
            weight_type=weight_type,
            weight_act=weight_act,
            linear_attention=linear_attention)

        # weights on skip-connection
        all_layer_attention_weight = model.get_all_layer_attention_weight()
        all_layer_ffn_weight = model.get_all_layer_ffn_weight()
        all_layer_attention_weight = [
            tf.reduce_mean(w) for w in all_layer_attention_weight
        ]
        all_layer_ffn_weight = [
            tf.reduce_mean(w) for w in all_layer_ffn_weight
        ]

        (masked_lm_loss, masked_lm_example_loss,
         masked_lm_log_probs) = get_masked_lm_output(
             bert_config, model.get_sequence_output(),
             model.get_embedding_table(), masked_lm_positions, masked_lm_ids,
             masked_lm_weights)

        (next_sentence_loss, next_sentence_example_loss,
         next_sentence_log_probs) = get_next_sentence_output(
             bert_config, model.get_pooled_output(), next_sentence_labels)

        total_loss = masked_lm_loss + next_sentence_loss

        def metric_fn(masked_lm_example_loss, masked_lm_log_probs,
                      masked_lm_ids, masked_lm_weights,
                      next_sentence_example_loss, next_sentence_log_probs,
                      next_sentence_labels):
            """Computes the loss and accuracy of the model."""
            masked_lm_log_probs = tf.reshape(
                masked_lm_log_probs, [-1, masked_lm_log_probs.shape[-1]])
            masked_lm_predictions = tf.argmax(masked_lm_log_probs,
                                              axis=-1,
                                              output_type=tf.int32)
            masked_lm_example_loss = tf.reshape(masked_lm_example_loss, [-1])
            masked_lm_ids = tf.reshape(masked_lm_ids, [-1])
            masked_lm_weights = tf.reshape(masked_lm_weights, [-1])
            masked_lm_accuracy = tf.metrics.accuracy(
                labels=masked_lm_ids,
                predictions=masked_lm_predictions,
                weights=masked_lm_weights)
            masked_lm_mean_loss = tf.metrics.mean(
                values=masked_lm_example_loss, weights=masked_lm_weights)

            next_sentence_log_probs = tf.reshape(
                next_sentence_log_probs,
                [-1, next_sentence_log_probs.shape[-1]])
            next_sentence_predictions = tf.argmax(next_sentence_log_probs,
                                                  axis=-1,
                                                  output_type=tf.int32)
            next_sentence_labels = tf.reshape(next_sentence_labels, [-1])
            next_sentence_accuracy = tf.metrics.accuracy(
                labels=next_sentence_labels,
                predictions=next_sentence_predictions)
            next_sentence_mean_loss = tf.metrics.mean(
                values=next_sentence_example_loss)

            # TODO: Add the perplexity measures. Should split a text set for evaluation.

            return {
                "masked_lm_accuracy": masked_lm_accuracy,
                "masked_lm_loss": masked_lm_mean_loss,
                "next_sentence_accuracy": next_sentence_accuracy,
                "next_sentence_loss": next_sentence_mean_loss,
            }

        # load variables from checkpoint if any
        tvars = tf.trainable_variables()
        initialized_variable_names = {}
        scaffold_fn = None
        if init_checkpoint:
            (assignment_map, initialized_variable_names
             ) = modeling.get_assignment_map_from_checkpoint(
                 tvars, init_checkpoint)
            if use_tpu:

                def tpu_scaffold():
                    tf.train.init_from_checkpoint(init_checkpoint,
                                                  assignment_map)
                    return tf.train.Scaffold()

                scaffold_fn = tpu_scaffold
            else:
                tf.train.init_from_checkpoint(init_checkpoint, assignment_map)

        tf.logging.info("**** Trainable Variables ****")
        for var in tvars:
            init_string = ""
            if var.name in initialized_variable_names:
                init_string = ", *INIT_FROM_CKPT*"
            tf.logging.info("  name = %s, shape = %s%s", var.name, var.shape,
                            init_string)

        output_spec = None
        if mode == tf.estimator.ModeKeys.TRAIN:
            train_op = optimization_hvd.create_optimizer(
                total_loss, learning_rate, num_train_steps, num_warmup_steps,
                use_tpu)

            metric = metric_fn(masked_lm_example_loss, masked_lm_log_probs,
                               masked_lm_ids, masked_lm_weights,
                               next_sentence_example_loss,
                               next_sentence_log_probs, next_sentence_labels)
            metric = {key: value[-1] for key, value in metric.items()}
            metric["total_loss"] = total_loss
            logging_hook = tf.train.LoggingTensorHook(tensors=metric,
                                                      every_n_iter=100)

            attention_weight_summary = [
                tf.summary.scalar("attention_weight_layer_{}".format(i),
                                  all_layer_attention_weight[i])
                for i in range(len(all_layer_attention_weight))
            ]
            ffn_weight_summary = [
                tf.summary.scalar("ffn_weight_layer_{}".format(i),
                                  all_layer_ffn_weight[i])
                for i in range(len(all_layer_ffn_weight))
            ]

            masked_lm_loss_summary = tf.summary.scalar("masked_lm_loss",
                                                       masked_lm_loss)
            next_sentence_loss_summary = tf.summary.scalar(
                "next_sentence_loss", next_sentence_loss)
            masked_lm_accuracy_summary = tf.summary.scalar(
                "masked_lm_accuracy", metric["masked_lm_accuracy"])
            next_sentence_accuracy_summary = tf.summary.scalar(
                "next_sentence_accuracy", metric["next_sentence_accuracy"])
            summary_hook = tf.train.SummarySaverHook(
                save_steps=100,
                output_dir=FLAGS.output_dir,
                summary_op=tf.summary.merge([
                    masked_lm_loss_summary, next_sentence_loss_summary,
                    masked_lm_accuracy_summary, next_sentence_accuracy_summary
                ] + attention_weight_summary + ffn_weight_summary))

            output_spec = tf.estimator.tpu.TPUEstimatorSpec(
                mode=mode,
                loss=total_loss,
                train_op=train_op,
                scaffold_fn=scaffold_fn,
                training_hooks=[logging_hook, summary_hook])

        elif mode == tf.estimator.ModeKeys.EVAL:

            eval_metrics = (metric_fn, [
                masked_lm_example_loss, masked_lm_log_probs, masked_lm_ids,
                masked_lm_weights, next_sentence_example_loss,
                next_sentence_log_probs, next_sentence_labels
            ])

            output_spec = tf.contrib.tpu.TPUEstimatorSpec(
                mode=mode,
                loss=total_loss,
                eval_metrics=eval_metrics,
                scaffold_fn=scaffold_fn)
        else:
            raise ValueError("Only TRAIN and EVAL modes are supported: %s" %
                             (mode))

        return output_spec