class_docstr: Multiwoz Evaluator. Now, we support metrics `'bleu'`
      
code: def _calc_metrics_info(self, generate_corpus, reference_corpus):
      i = 0
      data = deepcopy(self.data)
      for utt in data:
          utt["bspn_gen"] = generate_corpus.text[i * 3]
          utt["aspn_gen"] = generate_corpus.text[i * 3 + 1]
          utt["resp_gen"] = generate_corpus.text[i * 3 + 2]
          i += 1
      bleu, success, inform = self.eval.validation_metric(data)
      results = {
          "bleu": bleu,
          "success": success,
          "inform": inform,
          "overall": bleu + (success + inform) / 2,
      }
      return results
  
file_path: TextBox/textbox/evaluator/multiwoz_evaluator.py
imports: import json
  from copy import deepcopy
  from .abstract_evaluator import AbstractEvaluator
  from .utils.multiwoz.config import Config
  from .utils.multiwoz.reader import MultiWozReader
  from .utils.multiwoz.eval import MultiWozEvaluator
label_desc: Use image node_id 4 for calling the MultiwozEvaluator obj's underlying member method code with example usage: obj._calc_metrics_info(generate_corpus, reference_corpus) and returns: results