class_docstr: BPE Helper for GPT2 Models.
  
  Original source:
      https://github.com/openai/gpt-2/blob/main/src/encoder.py
  
  Original license: MIT
  
  This is a modified implementation from that of fairseq:
      https://github.com/pytorch/fairseq/blob/main/fairseq/data/encoders/gpt2_bpe_utils.py
  
  Fairseq license: MIT
class_docstr_tok: ["BPE","Helper","for","GPT2","Models",".","Original","source",":","https",":","\/\/github.com\/openai\/gpt-2\/blob\/main\/src\/encoder.py","Original","license",":","MIT","This","is","a","modified","implementation","from","that","of","fairseq",":","https",":","\/\/github.com\/pytorch\/fairseq\/blob\/main\/fairseq\/data\/encoders\/gpt2_bpe_utils.py","Fairseq","license",":","MIT"]
docstr: Return set of symbol pairs in a word.
  
  Word is represented as tuple of symbols (symbols being variable-length strings).
  
  :param word:
      word to symbolize
  
  :return pairs:
      set of tuples of symbols
docstr_tok: ["Return","set","of","symbol","pairs","in","a","word",".","Word","is","represented","as","tuple","of","symbols","(","symbols","being","variable-length","strings",")",".",":","param","word",":","word","to","symbolize",":","return","pairs",":","set","of","tuples","of","symbols"]
code: def get_pairs(self, word: Tuple[str, ...]) -> Set[Tuple[str, str]]:
      """
      Return set of symbol pairs in a word.
  
      Word is represented as tuple of symbols (symbols being variable-length strings).
  
      :param word:
          word to symbolize
  
      :return pairs:
          set of tuples of symbols
      """
      pairs = []
      prev_char = word[0]
      for char in word[1:]:
          pairs.append((prev_char, char))
          prev_char = char
      return pairs
  
imports: from parlai.core.params import ParlaiParser
  from abc import ABC, abstractmethod
  from functools import lru_cache
  import json
  import os
  import random
  import re
  from typing import Dict, List, Optional, Set, Tuple
  from typing_extensions import final
  from parlai.core.build_data import download, make_dir
  from parlai.core.opt import Opt
  from parlai.utils.misc import warn_once
  from parlai.utils.typing import TShared
  from parlai.utils.io import PathManager
  import parlai.utils.logging
label_desc: Use image node_id 5 for calling the Gpt2BpeHelper obj's underlying member method code with example usage: obj.get_pairs(word) and returns: pairs