def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'model_id') and self.model_id is not None:
            _dict['model_id'] = self.model_id
        if hasattr(self, 'name') and self.name is not None:
            _dict['name'] = self.name
        if hasattr(self, 'source') and self.source is not None:
            _dict['source'] = self.source
        if hasattr(self, 'target') and self.target is not None:
            _dict['target'] = self.target
        if hasattr(self, 'base_model_id') and self.base_model_id is not None:
            _dict['base_model_id'] = self.base_model_id
        if hasattr(self, 'domain') and self.domain is not None:
            _dict['domain'] = self.domain
        if hasattr(self, 'customizable') and self.customizable is not None:
            _dict['customizable'] = self.customizable
        if hasattr(self, 'default_model') and self.default_model is not None:
            _dict['default_model'] = self.default_model
        if hasattr(self, 'owner') and self.owner is not None:
            _dict['owner'] = self.owner
        if hasattr(self, 'status') and self.status is not None:
            _dict['status'] = self.status
        return _dict
Return a json dictionary representing this model.