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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 join(self, _id):
 """ Join a room """

        if not SockJSRoomHandler._room.has_key(self._gcls() + _id):
            SockJSRoomHandler._room[self._gcls() + _id] = set()
        SockJSRoomHandler._room[self._gcls() + _id].add(self)