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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 get_state_machine_selection(self):
 """An abstract getter method for state machine selection The method maybe has to be re-implemented by inherit classes and hands generally a filtered set of selected elements. :return: selection object it self, filtered set of selected elements :rtype: rafcon.gui.selection.Selection, set """

        sm_selection = self.model.get_state_machine_m().selection if self.model.get_state_machine_m() else None
        return sm_selection, sm_selection.get_selected_elements_of_core_class(self.CORE_ELEMENT_CLASS) if sm_selection else set()