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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 handle_unsubscribe(self, request):
 # type: (Unsubscribe) -> CallbackResponses """Handle a Unsubscribe request from outside. Called with lock taken"""

        subscribe = self._subscription_keys.pop(request.generate_key())
        ret = self._tree.handle_unsubscribe(subscribe, subscribe.path[1:])
        return ret