class_docstr: Check properties of an ongoing discourse.
class_docstr_tok: ["Check","properties","of","an","ongoing","discourse","."]
docstr: Remove a sentence from the current discourse.
  
  Updates ``self._input``, ``self._sentences`` and ``self._readings``.
  :param sentence: An input sentence
  :type sentence: str
  :param verbose: If ``True``,  report on the updated list of sentences.
code: def retract_sentence(self, sentence, verbose=True):
      """
      Remove a sentence from the current discourse.
  
      Updates ``self._input``, ``self._sentences`` and ``self._readings``.
      :param sentence: An input sentence
      :type sentence: str
      :param verbose: If ``True``,  report on the updated list of sentences.
      """
      try:
          self._input.remove(sentence)
      except ValueError:
          print(
              "Retraction failed. The sentence '%s' is not part of the current discourse:"
              % sentence
          )
          self.sentences()
          return None
      self._sentences = {
          "s%s" % i: sent for i, sent in enumerate(self._input)
      }
      self.readings(verbose=False)
      if verbose:
          print("Current sentences are ")
          self.sentences()
  
imports: import os
  from abc import ABCMeta, abstractmethod
  from functools import reduce
  from operator import add, and_
  from nltk.data import show_cfg
  from nltk.inference.mace import MaceCommand
  from nltk.inference.prover9 import Prover9Command
  from nltk.parse import load_parser
  from nltk.parse.malt import MaltParser
  from nltk.sem.drt import AnaphoraResolutionException, resolve_anaphora
  from nltk.sem.glue import DrtGlue
  from nltk.sem.logic import Expression
  from nltk.tag import RegexpTagger
label_desc: Use image node_id 4 for calling the DiscourseTester obj's underlying member method code with example usage: obj.retract_sentence(sentence, verbose) and returns: None