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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 add(self, **kwargs):
 """Adds a new element at the end of the list and returns it. Keyword arguments may be used to initialize the element. """

    new_element = self._message_descriptor._concrete_class(**kwargs)
    new_element._SetListener(self._message_listener)
    self._values.append(new_element)
    if not self._message_listener.dirty:
      self._message_listener.Modified()
    return new_element