Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'text') and self.text is not None:
            _dict['text'] = self.text
        if hasattr(self, '_additionalProperties'):
            for _key in self._additionalProperties:
                _value = getattr(self, _key, None)
                if _value is not None:
                    _dict[_key] = _value
        return _dict