code: def __call__(self, document, sentences_count):
      raise NotImplementedError(
          "This method should be overriden in subclass"
      )
  
file_path: sumy/sumy/summarizers/_summarizer.py
imports: from __future__ import absolute_import
  from __future__ import division, print_function, unicode_literals
  from collections import namedtuple
  from operator import attrgetter
  from ..utils import ItemsCount
  from .._compat import to_unicode
  from ..nlp.stemmers import null_stemmer
label_desc: Use image node_id 2 for calling the AbstractSummarizer obj's underlying member method code with example usage: obj.__call__(document, sentences_count) without return types