Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self,
                   'configuration_id') and self.configuration_id is not None:
            _dict['configuration_id'] = self.configuration_id
        if hasattr(self, 'name') and self.name is not None:
            _dict['name'] = self.name
        if hasattr(self, 'created') and self.created is not None:
            _dict['created'] = datetime_to_string(self.created)
        if hasattr(self, 'updated') and self.updated is not None:
            _dict['updated'] = datetime_to_string(self.updated)
        if hasattr(self, 'description') and self.description is not None:
            _dict['description'] = self.description
        if hasattr(self, 'conversions') and self.conversions is not None:
            _dict['conversions'] = self.conversions._to_dict()
        if hasattr(self, 'enrichments') and self.enrichments is not None:
            _dict['enrichments'] = [x._to_dict() for x in self.enrichments]
        if hasattr(self, 'normalizations') and self.normalizations is not None:
            _dict['normalizations'] = [
                x._to_dict() for x in self.normalizations
            ]
        if hasattr(self, 'source') and self.source is not None:
            _dict['source'] = self.source._to_dict()
        return _dict