svoid dynamicObject_dropRawField(DynamicObject o, O key) {
  if (o == null) ret;
  
  // double sync, but should be OK here because of locking order o > o.fieldValues
  synchronized(o) {
    // can drop the inner synchronization when we migrated all users
    // of fieldValues to synchronizing on the object too
    o.fieldValues = (LinkedHashMap) syncMapRemove_deleteMapIfEmpty((Map) o.fieldValues, key);
  }
}