class_docstr: A constraint representing a maximum allowed perturbed words.
      We use the lcs div the long of the sentence as the score.
  
  :param ~textflint.input.dataset origin_dataset:
          the dataset of origin sample
  :param ~textflint.input.dataset trans_dataset:
      the dataset of translate sample
  :param str|list fields: the name of the origin field need compare.
  :param bool need_tokens: if we need tokenize the sentence
code: def __repr__(self):
      return "MaxWordsPerturbed"
  
imports: import numpy
  from .validator import Validator
label_desc: Use image node_id 2 for calling the MaxWordsPerturbed obj's underlying member method code with example usage: obj.__repr__() and returns: str