def apply_GroupByKey(self, transform, pcoll):
    coder = self._get_coder(pcoll.element_type or typehints.Any)
    if not coder.is_kv_coder():
      raise ValueError(('Coder for the GroupByKey operation "%s" is not a '
                        'key-value coder: %s.') % (transform.label,
                                                   coder))
    # TODO(robertwb): Update the coder itself if it changed.
    coders.registry.verify_deterministic(
        coder.key_coder(), 'GroupByKey operation "%s"' % transform.label)

    return pvalue.PCollection(pcoll.pipeline)
dataset/ETHPy150Open GoogleCloudPlatform/DataflowPythonSDK/google/cloud/dataflow/runners/dataflow_runner.py/DataflowPipelineRunner.apply_GroupByKey/original