def SetSourceType(self, source_type):
    if self.source_type is None:
      self.source_type = source_type
Returns type/coder tuples for all custom types passed in.
dataset/ETHPy150Open log2timeline/dfvfs/dfvfs/helpers/source_scanner.py/SourceScannerContext.SetSourceType--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/DataflowPythonSDK/google/cloud/dataflow/coders/typecoders.py/CoderRegistry.get_custom_type_coder_tuples