@Nullable
  private static PropertiesFile toPropertiesFile(@Nullable final PsiFileSystemItem item) {
    if (item instanceof PropertiesFile) {
      return (PropertiesFile)item;
    }
    // Sometimes XmlPropertiesFile is just XmlFile, sao we should ask PropertiesImplUtil about that.
    return item instanceof PsiFile? PropertiesImplUtil.getPropertiesFile(((PsiFile)item)) : null;
  }
@Nullable
  private static PropertiesFile toPropertiesFile(@Nullable final PsiFileSystemItem item)