void doAdd(Map<String, T> toAdd) {
      if (toAdd == null) return;
      for (String url : toAdd.keySet()) {
        VirtualFile file = VirtualFileManager.getInstance().findFileByUrl(url);
        if (file == null) continue;
        setMapping(file, toAdd.get(url));
      }
    }
void doAdd(Map<String, T> toAdd)