Union[google.cloud.bigquery.ExternalConfig, None]: Configuration for
        an external data source (defaults to :data:`None`).

        Raises:
            ValueError: For invalid value types.

def external_data_configuration(self):
        """Union[google.cloud.bigquery.ExternalConfig, None]: Configuration for
        an external data source (defaults to :data:`None`).

        Raises:
            ValueError: For invalid value types.
        """
        prop = self._properties.get("externalDataConfiguration")
        if prop is not None:
            prop = ExternalConfig.from_api_repr(prop)
        return prop