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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 _unbind(self, rmq_server=None):
 """ Close AMQP connection and unset channel """

        try:
            self.connections[rmq_server].close()
        except AttributeError:
            pass

        self.connections[rmq_server] = None
        self.channels[rmq_server] = None