@Override
  public @Nullable DomFileElement<T> createMergedModelRoot(Set<? extends XmlFile> configFiles) {
    List<DomFileElement<T>> configs = new ArrayList<>(configFiles.size());
    for (XmlFile configFile : configFiles) {
      ContainerUtil.addIfNotNull(configs, getDomRoot(configFile));
    }
    return configs.isEmpty() ? null : getModelMerger().mergeModels(DomFileElement.class, configs);
  }
@Override
  public @Nullable DomFileElement<T> createMergedModelRoot(Set<? extends XmlFile> configFiles)