class_docstr: A negotiation teacher that loads the CaSiNo data from
  https://github.com/kushalchawla/CaSiNo.
  
  Each dialogue is converted into two datapoints, one from the perspective of each
  participant.
docstr: Process observation for metrics.
docstr_tok: ["Process","observation","for","metrics","."]
code: def observe(self, observation):
      """
      Process observation for metrics.
      """
      if self.expected_response is not None:
          self.metrics.evaluate_response(
              observation, self.expected_response
          )
          self.expected_response = None
      return observation
  
imports: from parlai.core.teachers import Teacher
  from .build import build
  from parlai.utils.io import PathManager
  import json
  import os
  import random
  import copy
label_desc: Use image node_id 7 for calling the CasinoTeacher obj's underlying member method code with example usage: obj.observe(observation) and returns: observation