# coding=utf-8
# Copyright 2020 Google and The HuggingFace Inc. team.
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# http://www.apache.org/licenses/LICENSE-2.0
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""" Tokenization class for model PEGASUS."""
import os
from shutil import copyfile
from typing import List, Optional, Tuple
from ...file_utils import is_sentencepiece_available
from ...tokenization_utils_fast import PreTrainedTokenizerFast
from ...utils import logging
if is_sentencepiece_available():
from .tokenization_pegasus import PegasusTokenizer
else:
PegasusTokenizer = None
logger = logging.get_logger(__name__)
SPIECE_UNDERLINE = "▁"
VOCAB_FILES_NAMES = {"vocab_file": "spiece.model", "tokenizer_file": "tokenizer.json"}
PRETRAINED_VOCAB_FILES_MAP = {
"vocab_file": {"google/pegasus-xsum": "https://huggingface.co/google/pegasus-xsum/resolve/main/spiece.model"},
"tokenizer_file": {
"google/pegasus-xsum": "https://huggingface.co/google/pegasus-xsum/resolve/main/tokenizer.json"
},
}
PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES = {
"google/pegasus-xsum": 512,
}
[docs]class PegasusTokenizerFast(PreTrainedTokenizerFast):
r"""
Construct a "fast" PEGASUS tokenizer (backed by HuggingFace's `tokenizers` library). Based on `Unigram
<https://huggingface.co/docs/tokenizers/python/latest/components.html?highlight=unigram#models>`__.
This tokenizer inherits from :class:`~transformers.PreTrainedTokenizerFast` which contains most of the main
methods. Users should refer to this superclass for more information regarding those methods.
Args:
vocab_file (:obj:`str`):
`SentencePiece <https://github.com/google/sentencepiece>`__ file (generally has a `.spm` extension) that
contains the vocabulary necessary to instantiate a tokenizer.
pad_token (:obj:`str`, `optional`, defaults to :obj:`"<pad>"`):
The token used for padding, for example when batching sequences of different lengths.
eos_token (:obj:`str`, `optional`, defaults to :obj:`"</s>"`):
The end of sequence token.
.. note::
When building a sequence using special tokens, this is not the token that is used for the end of
sequence. The token used is the :obj:`sep_token`.
unk_token (:obj:`str`, `optional`, defaults to :obj:`"<unk>"`):
The unknown token. A token that is not in the vocabulary cannot be converted to an ID and is set to be this
token instead.
mask_token (:obj:`str`, `optional`, defaults to :obj:`"<mask_2>"`):
The token used for masking single token values. This is the token used when training this model with masked
language modeling (MLM). This is the token that the PEGASUS encoder will try to predict during pretraining.
It corresponds to `[MASK2]` in `PEGASUS: Pre-training with Extracted Gap-sentences for Abstractive
Summarization <https://arxiv.org/pdf/1912.08777.pdf>`__.
mask_token_sent (:obj:`str`, `optional`, defaults to :obj:`"<mask_1>"`):
The token used for masking whole target sentences. This is the token used when training this model with gap
sentences generation (GSG). This is the sentence that the PEGASUS decoder will try to predict during
pretraining. It corresponds to `[MASK1]` in `PEGASUS: Pre-training with Extracted Gap-sentences for
Abstractive Summarization <https://arxiv.org/pdf/1912.08777.pdf>`__.
additional_special_tokens (:obj:`List[str]`, `optional`):
Additional special tokens used by the tokenizer. If no additional_special_tokens are provided <mask_2> and
<unk_2, ..., unk_102> are used as additional special tokens corresponding to the `original PEGASUS
tokenizer
<https://github.com/google-research/pegasus/blob/939830367bcf411193d2b5eca2f2f90f3f9260ca/pegasus/ops/pretrain_parsing_ops.cc#L66>`__
that uses the tokens 2 - 104 only for pretraining
"""
offset = 103 # entries 2-104 are only used for pretraining
vocab_files_names = VOCAB_FILES_NAMES
pretrained_vocab_files_map = PRETRAINED_VOCAB_FILES_MAP
max_model_input_sizes = PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES
slow_tokenizer_class = PegasusTokenizer
model_input_names = ["input_ids", "attention_mask"]
def __init__(
self,
vocab_file,
tokenizer_file=None,
pad_token="<pad>",
eos_token="</s>",
unk_token="<unk>",
mask_token="<mask_2>",
mask_token_sent="<mask_1>",
additional_special_tokens=None,
**kwargs
):
if additional_special_tokens is not None:
assert isinstance(
additional_special_tokens, list
), f"additional_special_tokens should be of type {type(list)}, but is {type(additional_special_tokens)}"
additional_special_tokens_extended = (
([mask_token_sent] + additional_special_tokens)
if mask_token_sent not in additional_special_tokens
else additional_special_tokens
)
# fill additional tokens with ..., <unk_token_102> in case not all additional tokens are already taken
additional_special_tokens_extended += [
f"<unk_{i}>" for i in range(len(additional_special_tokens_extended), self.offset - 1)
]
if len(set(additional_special_tokens_extended)) != len(additional_special_tokens_extended):
raise ValueError(
f"Please make sure that the provided additional_special_tokens do not contain an incorrectly shifted list of <unk_x> tokens. Found {additional_special_tokens_extended}."
)
additional_special_tokens = additional_special_tokens_extended
else:
additional_special_tokens = [mask_token_sent]
additional_special_tokens += [f"<unk_{i}>" for i in range(2, self.offset)]
super().__init__(
vocab_file,
tokenizer_file=tokenizer_file,
pad_token=pad_token,
eos_token=eos_token,
unk_token=unk_token,
mask_token=mask_token,
mask_token_sent=mask_token_sent,
additional_special_tokens=additional_special_tokens,
**kwargs,
)
self.vocab_file = vocab_file
def _special_token_mask(self, seq):
all_special_ids = set(self.all_special_ids) # call it once instead of inside list comp
all_special_ids.remove(self.unk_token_id) # <unk> is only sometimes special
assert all_special_ids == set(
range(len(self.additional_special_tokens) + 3)
), f"There should be 3 special tokens: mask_token, pad_token, and eos_token + {len(self.additional_special_tokens)} additional_special_tokens, but got {all_special_ids}"
return [1 if x in all_special_ids else 0 for x in seq]
[docs] def get_special_tokens_mask(
self, token_ids_0: List, token_ids_1: Optional[List] = None, already_has_special_tokens: bool = False
) -> List[int]:
"""Get list where entries are [1] if a token is [eos] or [pad] else 0."""
if already_has_special_tokens:
return self._special_token_mask(token_ids_0)
elif token_ids_1 is None:
return self._special_token_mask(token_ids_0) + [1]
else:
return self._special_token_mask(token_ids_0 + token_ids_1) + [1]
[docs] def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str] = None) -> Tuple[str]:
if not os.path.isdir(save_directory):
logger.error("Vocabulary path ({}) should be a directory".format(save_directory))
return
out_vocab_file = os.path.join(
save_directory, (filename_prefix + "-" if filename_prefix else "") + VOCAB_FILES_NAMES["vocab_file"]
)
if os.path.abspath(self.vocab_file) != os.path.abspath(out_vocab_file):
copyfile(self.vocab_file, out_vocab_file)
return (out_vocab_file,)