class_docstr: A mention (possible anaphor) inherite from spacy Span class with additional informations
docstr: Index of the sentence of the Mention in the current utterance
docstr_tok: ["Index","of","the","sentence","of","the","Mention","in","the","current","utterance"]
code: def _get_doc_sent_number(self):
      """Index of the sentence of the Mention in the current utterance"""
      for i, s in enumerate(self.doc.sents):
          if s == self.sent:
              return i
      return None
  
imports: import re
  import io
  from six import string_types, integer_types
  from spacy.tokens import Span, Token
  from neuralcoref.train.compat import unicode_
  from neuralcoref.train.utils import encode_distance, parallel_process
  import spacy
  import numpy
label_desc: Use image node_id 6 for calling the Mention obj's underlying member method code with example usage: obj._get_doc_sent_number() and returns: None, i