mrb_class_defined_under_id(mrb_state *mrb, struct RClass *outer, mrb_sym name)
{
  return mrb_const_defined_at(mrb, mrb_obj_value(outer), name);
}
mrb_class_defined_under_id(mrb_state *mrb, struct RClass *outer, mrb_sym name)
{
  return mrb_const_defined_at(mrb, mrb_obj_value(outer), name);
}