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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _GetByteStreamOperation(self):
 """Retrieves the byte stream operation. Returns: ByteStreamOperation: byte stream operation or None if unable to determine. """

    byte_order_string = self.GetStructByteOrderString()
    format_string = self.GetStructFormatString()  # pylint: disable=assignment-from-none
    if not format_string:
      return None

    format_string = ''.join([byte_order_string, format_string])
    return byte_operations.StructOperation(format_string)