tokenization_bn.py

"""
Forked from the file src/transformers/models/bert_generation/tokenization_bert_generation.py from the HuggingFace Transformers library.
Permalink: https://github.com/huggingface/transformers/blob/04ab5605fbb4ef207b10bf2772d88c53fc242e83/src/transformers/models/bert_generation/tokenization_bert_generation.py

"""
import os
import sentencepiece as spm
from shutil import copyfile
from transformers import PreTrainedTokenizer
from typing import Any, Dict, List, Optional, Tuple
VOCAB_FILES_NAMES = {'vocab_file': 'tokenizer.model'}

class BNTokenizer(PreTrainedTokenizer):
    """
      Construct a ReplitLMTokenizer tokenizer. Based on [SentencePiece](https://github.com/google/sentencepiece).
      This tokenizer inherits from [`PreTrainedTokenizer`] which contains most of the main methods.

      Args:
          vocab_file (`str`):
              [SentencePiece](https://github.com/google/sentencepiece) file (generally has a *.spm* extension) that
              contains the vocabulary necessary to instantiate a tokenizer.
          eos_token (`str`, *optional*, defaults to `"<|endoftext|>"`):
              The end of sequence token.
          bos_token (`str`, *optional*, defaults to `None`):
              The begin of sequence token.
          unk_token (`str`, *optional*, defaults to `"<|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.
          pad_token (`str`, *optional*, defaults to `"<|pad|>"`):
              The token used for padding, for example when batching sequences of different lengths.
          sp_model_kwargs (`dict`, *optional*):
              Will be passed to the `SentencePieceProcessor.__init__()` method. The [Python wrapper for
              SentencePiece](https://github.com/google/sentencepiece/tree/master/python) can be used, among other things,
              to set:
              - `enable_sampling`: Enable subword regularization.
              - `nbest_size`: Sampling parameters for unigram. Invalid for BPE-Dropout.
                - `nbest_size = {0,1}`: No sampling is performed.
                - `nbest_size > 1`: samples from the nbest_size results.
                - `nbest_size < 0`: assuming that nbest_size is infinite and samples from the all hypothesis (lattice)
                  using forward-filtering-and-backward-sampling algorithm.
              - `alpha`: Smoothing parameter for unigram sampling, and dropout probability of merge operations for
                BPE-dropout.
      """
    vocab_files_names = VOCAB_FILES_NAMES
    prefix_tokens: List[int] = []
    model_input_names = ['input_ids', 'attention_mask']

    def __init__(self, vocab_file, bos_token=None, eos_token='</s>', unk_token='<unk>', pad_token='<|reserved001|>', sep_token=None, sp_model_kwargs: Optional[Dict[str, Any]]=None, **kwargs) -> None:
        self.sp_model_kwargs = {} if sp_model_kwargs is None else sp_model_kwargs
        super().__init__(bos_token=bos_token, eos_token=eos_token, unk_token=unk_token, pad_token=pad_token, sep_token=sep_token, sp_model_kwargs=self.sp_model_kwargs, **kwargs)
        self.vocab_file = vocab_file
        self.sp_model = spm.SentencePieceProcessor(**self.sp_model_kwargs)
        self.sp_model.Load(vocab_file)

    @property
    def vocab_size(self):
        return self.sp_model.get_piece_size()

    def get_vocab(self):
        vocab = {self.convert_ids_to_tokens(i): i for i in range(self.vocab_size)}
        vocab.update(self.added_tokens_encoder)
        return vocab

    def __getstate__(self):
        state = self.__dict__.copy()
        state['sp_model'] = None
        return state

    def __setstate__(self, d):
        self.__dict__ = d
        if not hasattr(self, 'sp_model_kwargs'):
            self.sp_model_kwargs = {}
        self.sp_model = spm.SentencePieceProcessor(**self.sp_model_kwargs)
        self.sp_model.load(self.vocab_file)

    def _tokenize(self, text: str) -> List[str]:
        """Take as input a string and return a list of strings (tokens) for words/sub-words"""
        return self.sp_model.encode(text, out_type=str)

    def _convert_token_to_id(self, token):
        """Converts a token (str) in an id using the vocab."""
        return self.sp_model.piece_to_id(token)

    def _convert_id_to_token(self, index):
        """Converts an index (integer) in a token (str) using the vocab."""
        token = self.sp_model.id_to_piece(index)
        return token

    def convert_tokens_to_string(self, tokens):
        """Converts a sequence of tokens (string) in a single string."""
        return self.sp_model.decode(tokens)

    def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str]=None) -> Tuple[str]:
        if not os.path.isdir(save_directory):
            raise ValueError(f'Vocabulary path ({save_directory}) should be a directory')
        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) and os.path.isfile(self.vocab_file):
            copyfile(self.vocab_file, out_vocab_file)
        elif not os.path.isfile(self.vocab_file):
            with open(out_vocab_file, 'wb') as fi:
                content_spiece_model = self.sp_model.serialized_model_proto()
                fi.write(content_spiece_model)
        return (out_vocab_file,)