class_docstr: A class for tracking BLEU (https://www.aclweb.org/anthology/P02-1040.pdf).
  Arguments
  ---------
  merge_words: bool
      Whether to merge the successive words to create sentences.
  Example
  -------
  >>> bleu = BLEUStats()
  >>> i2l = {0: 'a', 1: 'b'}
  >>> bleu.append(
  ...     ids=['utterance1'],
  ...     predict=[[0, 1, 1]],
  ...     targets=[[[0, 1, 0]], [[0, 1, 1]], [[1, 1, 0]]],
  ...     ind2lab=lambda batch: [[i2l[int(x)] for x in seq] for seq in batch],
  ... )
  >>> stats = bleu.summarize()
  >>> stats['BLEU']
  0.0
docstr: Summarize the BLEU and return relevant statistics.
  * See MetricStats.summarize()
docstr_tok: ["Summarize","the","BLEU","and","return","relevant","statistics",".","*","See","MetricStats.summarize","(",")"]
code: def summarize(self, field=None):
      """Summarize the BLEU and return relevant statistics.
      * See MetricStats.summarize()
      """
  
      scores = self.bleu.corpus_score(self.predicts, self.targets)
      details = {}
      details["BLEU"] = scores.score
      details["BP"] = scores.bp
      details["ratio"] = scores.sys_len / scores.ref_len
      details["hyp_len"] = scores.sys_len
      details["ref_len"] = scores.ref_len
      details["precisions"] = scores.precisions
  
      self.scores = scores
      self.summary = details
  
      # Add additional, more generic key
      self.summary["bleu_score"] = self.summary["BLEU"]
  
      if field is not None:
          return self.summary[field]
      else:
          return self.summary
  
imports: from speechbrain.utils.metric_stats import MetricStats
label_desc: Use image node_id 3 for calling the BLEUStats obj's underlying member method code with example usage: obj.summarize(field) and returns: self, self