class_docstr: Constraint that uses the Google 1 Billion Words Language Model to
  determine the difference in perplexity between x and x_adv.
  
  Args:
      top_n (int):
      top_n_per_index (int):
      compare_against_original (bool):  If `True`, compare new `x_adv` against the original `x`.
          Otherwise, compare it against the previous `x_adv`.
code: def check_compatibility(self, transformation):
      return isinstance(transformation, WordSwap)
  
file_path: TextAttack/textattack/constraints/grammaticality/language_models/google_language_model/google_language_model.py
imports: from collections import defaultdict
  import numpy
  from textattack.constraints import Constraint
  from textattack.transformations import WordSwap
  from .alzantot_goog_lm import GoogLMHelper
label_desc: Use image node_id 2 for calling the GoogleLanguageModel obj's underlying member method code with example usage: obj.check_compatibility(transformation) and returns: isinstance