import os import json import regex as re from typing import Dict, List, Optional, Tuple, Union from transformers import PreTrainedTokenizer from transformers.utils import logging logger = logging.get_logger(__name__) class AksharaTokenizer(PreTrainedTokenizer): """ Akshara tokenizer for processing Indic language text. This tokenizer handles characters at the akshara (syllable) level. """ vocab_files_names = {"vocab_file": "vocab.json", "merges_file": "merges.txt"} model_input_names = ["input_ids", "attention_mask"] def __init__( self, vocab_file, merges_file=None, unk_token="", bos_token="", eos_token="", pad_token="", mask_token="", add_prefix_space=False, **kwargs ): super().__init__( unk_token=unk_token, bos_token=bos_token, eos_token=eos_token, pad_token=pad_token, mask_token=mask_token, add_prefix_space=add_prefix_space, **kwargs, ) # Load vocabulary with open(vocab_file, encoding="utf-8") as vocab_handle: self.encoder = json.load(vocab_handle) self.decoder = {v: k for k, v in self.encoder.items()} # Load merges if available self.merges = {} if merges_file is not None and os.path.isfile(merges_file): with open(merges_file, encoding="utf-8") as merges_handle: merges = merges_handle.read().split("\n") self.merges = {tuple(merge.split()): i for i, merge in enumerate(merges) if merge} # Special token handling self.add_prefix_space = add_prefix_space # Pre-compile regex patterns for tokenization self.pat = re.compile(r"""'s|'t|'re|'ve|'m|'ll|'d| ?\p{L}+| ?\p{N}+| ?[^\s\p{L}\p{N}]+|\s+(?!\S)|\s+""") @property def vocab_size(self): return len(self.encoder) def get_vocab(self): return dict(self.encoder, **self.added_tokens_encoder) def _tokenize(self, text): """Tokenize text into akshara units.""" if self.add_prefix_space and not text.startswith(" "): text = " " + text tokens = re.findall(self.pat, text) return tokens def _convert_token_to_id(self, token): """Convert a token to its ID in the vocabulary.""" return self.encoder.get(token, self.encoder.get(self.unk_token)) def _convert_id_to_token(self, index): """Convert an ID to its token in the vocabulary.""" return self.decoder.get(index, self.unk_token) def convert_tokens_to_string(self, tokens): """Convert a sequence of tokens to a single string.""" text = "".join(tokens) text = text.replace(" ", "").replace("▁", " ").strip() return text def build_inputs_with_special_tokens(self, token_ids_0, token_ids_1=None): """Build model inputs from a sequence by appending eos_token_id.""" if token_ids_1 is None: return [self.bos_token_id] + token_ids_0 + [self.eos_token_id] return [self.bos_token_id] + token_ids_0 + [self.eos_token_id] + token_ids_1 + [self.eos_token_id] def get_special_tokens_mask(self, token_ids_0, token_ids_1=None, already_has_special_tokens=False): """Get list where entries are [1] if a token is special and [0] otherwise.""" if already_has_special_tokens: return super().get_special_tokens_mask( token_ids_0=token_ids_0, token_ids_1=token_ids_1, already_has_special_tokens=True ) if token_ids_1 is None: return [1] + ([0] * len(token_ids_0)) + [1] return [1] + ([0] * len(token_ids_0)) + [1] + ([0] * len(token_ids_1)) + [1] def create_token_type_ids_from_sequences(self, token_ids_0, token_ids_1=None): """Create a mask from the two sequences for sequence classification tasks.""" eos = [self.eos_token_id] bos = [self.bos_token_id] if token_ids_1 is None: return len(bos + token_ids_0 + eos) * [0] return len(bos + token_ids_0 + eos) * [0] + len(token_ids_1 + eos) * [1] def save_vocabulary(self, save_directory, filename_prefix=None): """Save the vocabulary and merges files to a directory.""" if not os.path.isdir(save_directory): logger.error(f"Vocabulary path ({save_directory}) should be a directory") return vocab_file = os.path.join( save_directory, (filename_prefix + "-" if filename_prefix else "") + self.vocab_files_names["vocab_file"] ) with open(vocab_file, "w", encoding="utf-8") as f: f.write(json.dumps(self.encoder, ensure_ascii=False)) return (vocab_file,) # Register the tokenizer with the AutoTokenizer class from transformers import AutoTokenizer AutoTokenizer.register("akshara", AksharaTokenizer) # Register the model configuration if needed from transformers.models.auto.configuration_auto import CONFIG_MAPPING if "akshara" not in CONFIG_MAPPING: from transformers import PretrainedConfig class AksharaConfig(PretrainedConfig): model_type = "akshara" CONFIG_MAPPING.register("akshara", AksharaConfig)