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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 clone(self, screen, scene):
 """ Create a clone of this Dialog into a new Screen. :param screen: The new Screen object to clone into. :param scene: The new Scene object to clone into. """

        # Only clone the object if the function is safe to do so.
        if self._on_close is None or isfunction(self._on_close):
            scene.add_effect(PopUpDialog(screen, self._text, self._buttons, self._on_close))