class_docstr: An abstract class that takes a sentence and transforms it by replacing
  some of its words.
  
  letters_to_insert (string): letters allowed for insertion into words
  (used by some char-based transformations)
docstr: Returns a set of replacements given an input word. Must be overriden
  by specific word swap transformations.
  
  Args:
      word: The input word to find replacements for.
code: def _get_replacement_words(self, word):
      """Returns a set of replacements given an input word. Must be overriden
      by specific word swap transformations.
  
      Args:
          word: The input word to find replacements for.
      """
      raise NotImplementedError()
  
file_path: TextAttack/textattack/transformations/word_swaps/word_swap.py
imports: import random
  import string
  from textattack.transformations import Transformation
label_desc: Use image node_id 2 for calling the WordSwap obj's underlying member method code with example usage: obj._get_replacement_words(word) without return types