svoid metaMapPut(IMeta o, O key, O value) {
  if (o == null || key == null) ret;
  Map map = convertObjectMetaToMap(o);
  syncMapPutOrRemove(map, key, value);
}

// untested...
/*svoid metaMapPut(IMeta o, O key, O value, IMapImplementationPolicy policy) {
  if (o == null || key == null) ret;
  if (policy == null) ret with metaMapPut(o, key, value);
  
  // no shortcuts in this function, always get mutex & lock
  temp var mutex = tempMetaMutex(o);
  synchronized(mutex!) {
    O meta = o._getMeta();
    
    // create map if necessary
    Map map = null;
    if (meta cast Map)
      map = meta;
    else if (meta != null)
      map = policy.put(map, previousMeta := meta);
      
    // putOrRemove through policy
    if (value != null)
      map = policy.put(map, key, value);
    else
      map = policy.remove(map, key);
      
    if (map != meta) o._setMeta(map);
  }
}*/

Began life as a copy of #1031852