sO dm_resetField(S field, O mod) {
  mod = dm_getModule(mod);
  if (mod == null) ret;
  O tempInstance = newInstance(mod.getClass());
  try {
    O value = getOpt(tempInstace, field);
    dm_setOpt(mod, value);
  } finally {
    cleanUp(tempInstance);
  }
  ret value;
}