code: def rouge_1(evaluated_sentences, reference_sentences):
      """
      Rouge-N where N=1.  This is a commonly used metric.
  
      :param evaluated_sentences:
          The sentences that have been picked by the summarizer
      :param reference_sentences:
          The sentences from the reference set
      :returns:
          float 0 <= ROUGE-N <= 1, where 0 means no overlap and 1 means
          exactly the same.
      """
      return rouge_n(evaluated_sentences, reference_sentences, 1)
  
file_path: sumy/sumy/evaluation/rouge.py
imports: from __future__ import absolute_import
  from __future__ import division, print_function, unicode_literals
  from ..models.dom import Sentence
label_desc: Use image node_id 9 for calling a global function with example usage: rouge_1(evaluated_sentences, reference_sentences) and returns: rouge_n