Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'message_type') and self.message_type is not None:
            _dict['message_type'] = self.message_type
        if hasattr(self, 'text') and self.text is not None:
            _dict['text'] = self.text
        if hasattr(self, 'options') and self.options is not None:
            _dict['options'] = self.options._to_dict()
        if hasattr(self, 'intents') and self.intents is not None:
            _dict['intents'] = [x._to_dict() for x in self.intents]
        if hasattr(self, 'entities') and self.entities is not None:
            _dict['entities'] = [x._to_dict() for x in self.entities]
        if hasattr(self, 'suggestion_id') and self.suggestion_id is not None:
            _dict['suggestion_id'] = self.suggestion_id
        return _dict