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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 extend(self, elem_seq):
 """Extends by appending the given sequence of elements of the same type as this one, copying each individual message. """

    message_class = self._message_descriptor._concrete_class
    listener = self._message_listener
    values = self._values
    for message in elem_seq:
      new_element = message_class()
      new_element._SetListener(listener)
      new_element.MergeFrom(message)
      values.append(new_element)
    listener.Modified()