prec.c:53
static VALUE
prec_included(module, include)
    VALUE module, include;
{
    switch (TYPE(include)) {
      case T_CLASS:
      case T_MODULE:
       break;
      default:
       Check_Type(include, T_CLASS);
       break;
    }
    rb_define_singleton_method(include, "induced_from", prec_induced_from, 1);
    return module;
}
