def classifier_model(
model_config: xlnet_config.XLNetConfig,
run_config: xlnet_config.RunConfig,
num_labels: int,
final_layer_initializer: tf.keras.initializers.Initializer = None
) -> tf.keras.Model:
"""Returns a TF2 Keras XLNet classifier model.
Construct a Keras model for predicting `num_labels` outputs from an input with
maximum sequence length `max_seq_length`.
Args:
model_config: the config that defines the core XLNet model.
run_config: separate runtime configuration with extra parameters.
num_labels: integer, the number of classes.
final_layer_initializer: Initializer for final dense layer. If `None`, then
it defaults to the one specified in `run_config`.
Returns:
Combined prediction model inputs -> (one-hot labels)
XLNet sub-model inputs -> (xlnet_outputs)
where inputs are:
(words, segments, mask, permutation mask,
target mapping, masked tokens)
"""
if final_layer_initializer is not None:
initializer = final_layer_initializer
else:
initializer = tf.keras.initializers.RandomNormal(mean=0., stddev=.02)
xlnet_base = get_xlnet_base(model_config=model_config,
run_config=run_config,
attention_type='bi',
two_stream=False,
use_cls_mask=False)
return models.XLNetClassifier(network=xlnet_base,
num_classes=num_labels,
dropout_rate=run_config.dropout,
summary_type='last',
initializer=initializer), xlnet_base
def build_model(self):
if self.task_config.hub_module_url and self.task_config.init_checkpoint:
raise ValueError('At most one of `hub_module_url` and '
'`init_checkpoint` can be specified.')
if self.task_config.hub_module_url:
encoder_network = utils.get_encoder_from_hub(
self.task_config.hub_module_url)
else:
encoder_network = encoders.build_encoder(self.task_config.model.encoder)
encoder_cfg = self.task_config.model.encoder.get()
if self.task_config.model.encoder.type == 'xlnet':
return models.XLNetClassifier(
network=encoder_network,
num_classes=self.task_config.model.num_classes,
initializer=tf.keras.initializers.RandomNormal(
stddev=encoder_cfg.initializer_range))
else:
return models.BertClassifier(
network=encoder_network,
num_classes=self.task_config.model.num_classes,
initializer=tf.keras.initializers.TruncatedNormal(
stddev=encoder_cfg.initializer_range),
use_encoder_pooler=self.task_config.model.use_encoder_pooler)
