docstr: calculate the language model score
docstr_tok: ["calculate","the","language","model","score"]
code: def calc_lm_score(self, phrase_list):
      """calculate the language model score"""
      lm_score = 0.0
      if len(phrase_list) == 0:
          return 0.0
      for phrase in phrase_list:
          lm_score += self.ngram_dict.get(phrase, self.oov_score)
      return lm_score / len(phrase_list)
  
imports: import io
  import numpy
  import six
label_desc: Use image node_id 5 for calling the Interventer obj's underlying member method code with example usage: obj.calc_lm_score(phrase_list) and returns: unknown, int