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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:
 async def unregister(self, channel, event, callback):
 """Safely unregister a callback from the list of ``event`` callbacks for ``channel_name``. :param channel: channel name :param event: event name :param callback: callback to execute when event on channel occurs :return: a coroutine which results in the channel object where the ``callback`` was removed (if found) """

        channel = self.channel(channel, create=False)
        if channel:
            channel.unregister(event, callback)
            if not channel:
                await channel.disconnect()
                self.channels.pop(channel.name)
        return channel