public static void collectUnknownNatures(String path, Map<String, String> naturesNames, String separator) {
    Set<String> natures = collectNatures(path);
    natures.removeAll(EclipseNatureImporter.getDefaultNatures());

    for (EclipseNatureImporter importer : EclipseNatureImporter.EP_NAME.getExtensions()) {
      natures.remove(importer.getNatureName());
    }

    if (!natures.isEmpty()) {
      naturesNames.put(path, StringUtil.join(natures, separator));
    }
  }
public static void collectUnknownNatures(String path, Map<String, String> naturesNames, String separator)