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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 _CheckFieldMaskMessage(message):
 """Raises ValueError if message is not a FieldMask."""

  message_descriptor = message.DESCRIPTOR
  if (message_descriptor.name != 'FieldMask' or
      message_descriptor.file.name != 'google/protobuf/field_mask.proto'):
    raise ValueError('Message {0} is not a FieldMask.'.format(
        message_descriptor.full_name))