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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 backend_disable(cls, backend):
 """ Disable a backend for a server """

        server = cls.backend_list(backend)
        oper = cls.call('hosting.rproxy.server.disable',
                        server[0]['id'])
        cls.echo('Desactivating backend on server %s' %
                 server[0]['ip'])
        cls.display_progress(oper)
        cls.echo('Backend desactivated')
        return oper