svoid dynamicObject_dropRawField(DynamicObject o, O key, O value) {
  if (o == null) ret;
  
  // double sync, but should be OK here because of locking order o > o.fieldValues
  synchronized(o) {
    o.fieldValues = syncMapRemove_deleteMapIfEmpty((LinkedHashMap) o.fieldValues, key, value);
  }
}