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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 _BuildMessageFromTypeName(type_name, descriptor_pool):
 """Returns a protobuf message instance. Args: type_name: Fully-qualified protobuf message type name string. descriptor_pool: DescriptorPool instance. Returns: A Message instance of type matching type_name, or None if the a Descriptor wasn't found matching type_name. """

  # pylint: disable=g-import-not-at-top
  from google.protobuf import symbol_database
  database = symbol_database.Default()
  try:
    message_descriptor = descriptor_pool.FindMessageTypeByName(type_name)
  except KeyError:
    return None
  message_type = database.GetPrototype(message_descriptor)
  return message_type()