def __init__(self, params):
if bool(params.tfds_name) == bool(params.input_path):
raise ValueError(
'Must specify either `tfds_name` and `tfds_split` '
'or `input_path`.')
if bool(params.vocab_file) == bool(
params.preprocessing_hub_module_url):
raise ValueError(
'Must specify exactly one of vocab_file (with matching '
'lower_case flag) or preprocessing_hub_module_url.')
self._params = params
self._seq_length = params.seq_length
self._left_text_fields = params.left_text_fields
self._right_text_fields = params.right_text_fields
if params.preprocessing_hub_module_url:
preprocessing_hub_module = hub.load(
params.preprocessing_hub_module_url)
self._tokenizer = preprocessing_hub_module.tokenize
self._pack_inputs = functools.partial(
preprocessing_hub_module.bert_pack_inputs,
seq_length=params.seq_length)
else:
self._tokenizer = layers.BertTokenizer(
vocab_file=params.vocab_file, lower_case=params.lower_case)
self._pack_inputs = layers.BertPackInputs(
seq_length=params.seq_length,
special_tokens_dict=self._tokenizer.get_special_tokens_dict())
def create_preprocessing(*,
vocab_file: Optional[str] = None,
sp_model_file: Optional[str] = None,
do_lower_case: bool,
tokenize_with_offsets: bool,
default_seq_length: int) -> tf.keras.Model:
"""Returns a preprocessing Model for given tokenization parameters.
This function builds a Keras Model with attached subobjects suitable for
saving to a SavedModel. The resulting SavedModel implements the Preprocessor
API for Text embeddings with Transformer Encoders described at
https://www.tensorflow.org/hub/common_saved_model_apis/text.
Args:
vocab_file: The path to the wordpiece vocab file, or None.
sp_model_file: The path to the sentencepiece model file, or None.
Exactly one of vocab_file and sp_model_file must be set.
This determines the type of tokenzer that is used.
do_lower_case: Whether to do lower case.
tokenize_with_offsets: Whether to include the .tokenize_with_offsets
subobject.
default_seq_length: The sequence length of preprocessing results from
root callable. This is also the default sequence length for the
bert_pack_inputs subobject.
Returns:
A tf.keras.Model object with several attached subobjects, suitable for
saving as a preprocessing SavedModel.
"""
# Select tokenizer.
if bool(vocab_file) == bool(sp_model_file):
raise ValueError("Must set exactly one of vocab_file, sp_model_file")
if vocab_file:
tokenize = layers.BertTokenizer(
vocab_file=vocab_file,
lower_case=do_lower_case,
tokenize_with_offsets=tokenize_with_offsets)
else:
tokenize = layers.SentencepieceTokenizer(
model_file_path=sp_model_file,
lower_case=do_lower_case,
strip_diacritics=True, # Strip diacritics to follow ALBERT model.
tokenize_with_offsets=tokenize_with_offsets)
# The root object of the preprocessing model can be called to do
# one-shot preprocessing for users with single-sentence inputs.
sentences = tf.keras.layers.Input(shape=(),
dtype=tf.string,
name="sentences")
if tokenize_with_offsets:
tokens, start_offsets, limit_offsets = tokenize(sentences)
else:
tokens = tokenize(sentences)
pack = layers.BertPackInputs(
seq_length=default_seq_length,
special_tokens_dict=tokenize.get_special_tokens_dict())
model_inputs = pack(tokens)
preprocessing = tf.keras.Model(sentences, model_inputs)
# Individual steps of preprocessing are made available as named subobjects
# to enable more general preprocessing. For saving, they need to be Models
# in their own right.
preprocessing.tokenize = tf.keras.Model(sentences, tokens)
# Provide an equivalent to tokenize.get_special_tokens_dict().
preprocessing.tokenize.get_special_tokens_dict = tf.train.Checkpoint()
preprocessing.tokenize.get_special_tokens_dict.__call__ = tf.function(
lambda: tokenize.get_special_tokens_dict(), # pylint: disable=[unnecessary-lambda]
input_signature=[])
if tokenize_with_offsets:
preprocessing.tokenize_with_offsets = tf.keras.Model(
sentences, [tokens, start_offsets, limit_offsets])
preprocessing.tokenize_with_offsets.get_special_tokens_dict = (
preprocessing.tokenize.get_special_tokens_dict)
# Conceptually, this should be
# preprocessing.bert_pack_inputs = tf.keras.Model(tokens, model_inputs)
# but technicalities require us to use a wrapper (see comments there).
# In particular, seq_length can be overridden when calling this.
preprocessing.bert_pack_inputs = BertPackInputsSavedModelWrapper(pack)
return preprocessing