class_docstr: A conversational dialog chat bot.
docstr: Learn that the statement provided is a valid response.
code: def learn_response(self, statement, previous_statement=None):
      """
      Learn that the statement provided is a valid response.
      """
      if not previous_statement:
          previous_statement = statement.in_response_to
  
      if not previous_statement:
          previous_statement = self.get_latest_response(
              statement.conversation
          )
          if previous_statement:
              previous_statement = previous_statement.text
  
      previous_statement_text = previous_statement
  
      if not isinstance(
          previous_statement,
          (
              str,
              type(None),
          ),
      ):
          statement.in_response_to = previous_statement.text
      elif isinstance(previous_statement, str):
          statement.in_response_to = previous_statement
  
      self.logger.info(
          'Adding "{}" as a response to "{}"'.format(
              statement.text, previous_statement_text
          )
      )
  
      # Save the input statement
      return self.storage.create(**statement.serialize())
  
file_path: ChatterBot/chatterbot/chatterbot.py
imports: import logging
  from chatterbot.storage import StorageAdapter
  from chatterbot.logic import LogicAdapter
  from chatterbot.search import TextSearch, IndexedTextSearch
  from chatterbot import utils
label_desc: Use image node_id 4 for calling the ChatBot obj's underlying member method code with example usage: obj.learn_response(statement, previous_statement) and returns: self