sbool dm_isFirstSiblingModule_debug;

sbool dm_isFirstSiblingModule(O mod) {
  S libID = dm_moduleLibID(mod);
  if (libID == null) false;
  LS siblings = dm_modulesWithLibID(libID);
  if (dm_isFirstSiblingModule_debug)
    printVars(+libID, +siblings);
  if (empty(siblings)) true; // no idea why this happens sometimes
  ret eq(dm_moduleID(mod), lowestByAlphaNum(siblings));
}