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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):
 """Getter state machine selection :return: selection object, filtered set of selected states :rtype: rafcon.gui.selection.Selection, set """

        if self._selected_sm_model:
            return self._selected_sm_model.selection, self._selected_sm_model.selection.states
        else:
            return None, set()