class_docstr: Transforms an input by replacing its words with antonyms provided by
  WordNet. Download nltk_data before running.
  
  Implement follow by Stress Test Evaluation for Natural Language Inference
  For the correctness of trasformation we swap the word has best_sense(
  Wordnet) to its antonym
  
  https://www.aclweb.org/anthology/C18-1198/
  
  exmaple:
  {
      hypothesis: I hate this book.
      premise: This book is my favorite.
      label: contradiction
  }
code: def __repr__(self):
      return "SwapAnt"
  
file_path: textflint/textflint/generation/transformation/NLI/swap_ant.py
imports: from nltk.wsd import lesk
  from ..transformation import Transformation
  from ....common.settings import BLACK_LIST_WORD
label_desc: Use image node_id 2 for calling the SwapAnt obj's underlying member method code with example usage: obj.__repr__() and returns: str