Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'name') and self.name is not None:
            _dict['name'] = self.name
        if hasattr(self,
                   'dbpedia_resource') and self.dbpedia_resource is not None:
            _dict['dbpedia_resource'] = self.dbpedia_resource
        if hasattr(self, 'subtype') and self.subtype is not None:
            _dict['subtype'] = self.subtype
        return _dict