docs: def _from_dict(cls, _dict):
          """Initialize a Context object from a json dictionary."""
          args = {}
          xtra = _dict.copy()
          if 'conversation_id' in _dict:
              args['conversation_id'] = _dict.get('conversation_id')
              del xtra['conversation_id']
          if 'system' in _dict:
              args['system'] = SystemResponse._from_dict(_dict.get('system'))
              del xtra['system']
          if 'metadata' in _dict:
              args['metadata'] = MessageContextMetadata._from_dict(
                  _dict.get('metadata'))
              del xtra['metadata']
          args.update(xtra)
          return cls(**args)