@Nullable
  static String getGuardValue(PsiDocTag tag) {
    if ("GuardedBy".equals(tag.getName())) {
      final PsiDocTagValue value = tag.getValueElement();
      if (value == null) return "";
      return resolveItself(value.getText(), tag);
    }
    else {
      final String text = tag.getText();
      if (!text.startsWith("@GuardedBy")) return null;
      int start = text.indexOf('(');
      int end = text.indexOf(')');
      if (start >= end || start < 0) return "";
      return resolveItself(text.substring(start + 1, end), tag);
    }
  }
@Nullable
  static String getGuardValue(PsiDocTag tag)