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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 keystrokeReceived(self, keyID, modifier):
 """ Forward input events to the application-supplied protocol if one is currently active, otherwise forward them to the main menu UI. """

        if self._protocol is not None:
            self._protocol.keystrokeReceived(keyID, modifier)
        else:
            self._window.keystrokeReceived(keyID, modifier)