Generate a resource for :meth:`_begin`.

def to_api_repr(self):
        """Generate a resource for :meth:`_begin`."""

        source_ref = {
            "projectId": self.source.project,
            "datasetId": self.source.dataset_id,
            "tableId": self.source.table_id,
        }

        configuration = self._configuration.to_api_repr()
        _helpers._set_sub_prop(configuration, ["extract", "sourceTable"], source_ref)
        _helpers._set_sub_prop(
            configuration, ["extract", "destinationUris"], self.destination_uris
        )

        return {
            "jobReference": self._properties["jobReference"],
            "configuration": configuration,
        }