class_docstr: Abstract class representing word embedding used by TextAttack.
  
  This class specifies all the methods that is required to be defined
  so that it can be used for transformation and constraints. For
  custom word embedding not supported by TextAttack, please create a
  class that inherits this class and implement the required methods.
  However, please first check if you can use `WordEmbedding` class,
  which has a lot of internal methods implemented.
class_docstr_tok: ["Abstract","class","representing","word","embedding","used","by","TextAttack",".","This","class","specifies","all","the","methods","that","is","required","to","be","defined","so","that","it","can","be","used","for","transformation","and","constraints",".","For","custom","word","embedding","not","supported","by","TextAttack",",","please","create","a","class","that","inherits","this","class","and","implement","the","required","methods",".","However",",","please","first","check","if","you","can","use","`","WordEmbedding","`","class",",","which","has","a","lot","of","internal","methods","implemented","."]
docstr: Convert index to corresponding word
  Args:
      index (int)
  Returns:
      word (str)
docstr_tok: ["Convert","index","to","corresponding","word","Args",":","index","(","int",")","Returns",":","word","(","str",")"]
code: def index2word(self, index):
      """
      Convert index to corresponding word
      Args:
          index (int)
      Returns:
          word (str)
      """
      raise NotImplementedError()
  
imports: from abc import ABC, abstractmethod
  from collections import defaultdict
  import os
  import pickle
  import numpy
  import torch
  from textattack.shared import utils
label_desc: Use image node_id 5 for calling the AbstractWordEmbedding obj's underlying member method code with example usage: obj.index2word(index) without return types