code: def get_bleu(a, b):
      ref = a.words
      hyp = b.words
      bleu_score = nltk.translate.bleu_score.sentence_bleu([ref], hyp)
      return bleu_score
  
file_path: TextAttack/textattack/goal_functions/text/minimize_bleu.py
imports: import functools
  import nltk
  import textattack
  from .text_to_text_goal_function import TextToTextGoalFunction
label_desc: Use image node_id 1 for calling a global function with example usage: get_bleu(a, b) and returns: bleu_score