return clonespec only if values are valid

def get_clonespec_for_valid_snapshot(config_spec, object_ref, reloc_spec, template, vm_):
    '''
    return clonespec only if values are valid
    '''
    moving = True
    if QUICK_LINKED_CLONE == vm_['snapshot']['disk_move_type']:
        reloc_spec.diskMoveType = QUICK_LINKED_CLONE
    elif CURRENT_STATE_LINKED_CLONE == vm_['snapshot']['disk_move_type']:
        reloc_spec.diskMoveType = CURRENT_STATE_LINKED_CLONE
    elif COPY_ALL_DISKS_FULL_CLONE == vm_['snapshot']['disk_move_type']:
        reloc_spec.diskMoveType = COPY_ALL_DISKS_FULL_CLONE
    elif FLATTEN_DISK_FULL_CLONE == vm_['snapshot']['disk_move_type']:
        reloc_spec.diskMoveType = FLATTEN_DISK_FULL_CLONE
    else:
        moving = False

    if moving:
        return build_clonespec(config_spec, object_ref, reloc_spec, template)

    return None