def find_orphaned_vdi_uuids(xenapi):
    """Walk VM -> VBD -> VDI change and accumulate connected VDIs."""
    connected_vdi_uuids = set()

    _find_vdis_connected_to_vm(xenapi, connected_vdi_uuids)

    all_vdi_uuids = set()
    _find_all_vdis_and_system_vdis(xenapi, all_vdi_uuids, connected_vdi_uuids)

    orphaned_vdi_uuids = connected_vdi_uuids - all_vdi_uuids
    return orphaned_vdi_uuids
dataset/ETHPy150Open openstack/nova/tools/xenserver/vm_vdi_cleaner.py/find_orphaned_vdi_uuids/swapped operands of `-`