class_docstr: Bleu scorer.
class_docstr_tok: ["Bleu","scorer","."]
code: def single_reflen(self, option="average"):
      return self._single_reflen(self.crefs[0][0], option)
  
imports: import copy
  import math
  from builtins import dict, range
  from collections import defaultdict
label_desc: Use image node_id 14 for calling the BleuScorer obj's underlying member method code with example usage: obj.single_reflen(option) and returns: self