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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 _detach(cls, iface_id):
 """ Detach an iface from a vm. """

        iface = cls._info(iface_id)
        opers = []
        vm_id = iface.get('vm_id')
        if vm_id:
            cls.echo('The iface is still attached to the vm %s.' % vm_id)
            cls.echo('Will detach it.')
            opers.append(cls.call('hosting.vm.iface_detach', vm_id, iface_id))
        return opers