Initialize a MessageResponse object from a json dictionary.

def _from_dict(cls, _dict):
        """Initialize a MessageResponse object from a json dictionary."""
        args = {}
        if 'output' in _dict:
            args['output'] = MessageOutput._from_dict(_dict.get('output'))
        else:
            raise ValueError(
                'Required property \'output\' not present in MessageResponse JSON'
            )
        if 'context' in _dict:
            args['context'] = MessageContext._from_dict(_dict.get('context'))
        return cls(**args)