class_docstr: Base class for BLEU & NIST, providing tokenization and some basic n-gram matching
  functions.
docstr: Compute the current score based on sentences added so far.
docstr_tok: ["Compute","the","current","score","based","on","sentences","added","so","far","."]
code: def score(self):
      """Compute the current score based on sentences added so far."""
      raise NotImplementedError()
  
imports: from __future__ import unicode_literals
  from __future__ import division
  from builtins import zip
  from builtins import range
  from past.utils import old_div
  from builtins import object
  from collections import defaultdict
  import math
  import re
label_desc: Use image node_id 4 for calling the NGramScore obj's underlying member method code with example usage: obj.score() without return types