def _get_unused_nets(self, vms_to_stop):
        """
        Return a list of nets that used only by the vms in vms_to_stop
        Args:
            vms_to_stop (list of str): The names of the requested vms
        Returns
            list of virt.Network: net objects that used only by
                vms in vms_to_stop
        Raises:
            utils.LagoUserException: If a vm name doesn't exist
        """

        vm_names = [vm.name() for vm in vms_to_stop]
        unused_nets = set()

        for vm in vms_to_stop:
            unused_nets = unused_nets.union(vm.nets())
        for vm in self._vms.values():
            if not vm.running() or vm.name() in vm_names:
                continue
            for net in vm.nets():
                unused_nets.discard(net)
        nets = [self._nets[net] for net in unused_nets]

        return nets
Return a list of nets that used only by the vms in vms_to_stop
        Args:
            vms_to_stop (list of str): The names of the requested vms
        Returns
            list of virt.Network: net objects that used only by
                vms in vms_to_stop
        Raises:
            utils.LagoUserException: If a vm name doesn't exist