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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 subscribe(self, channel):
 """ Add the channel to this socket's channels, and to the list of subscribed session IDs for the channel. Return False if already subscribed, otherwise True. """

        if channel in self.channels:
            return False
        CHANNELS[channel].append(self.socket.session.session_id)
        self.channels.append(channel)
        return True