def METHOD_NAME(lines, all_nm):
    errors  = []
    xr      = sorted(set(extract(lines, '.Xr', '3monocypher')))
    dead_xr = [x for x in xr if all_nm.count(x) == 0]
    if len(dead_xr) > 0:
        errors.append('Dead .Xr: ' + str(dead_xr))
    return errors