static RegExpGroup resolve(int index, PsiFile file) {
        if (index < 0) {
            return resolveRelativeGroup(Math.abs(index), file);
        }

        return SyntaxTraverser.psiTraverser(file)
          .filter(RegExpGroup.class)
          .filter(RegExpGroup::isCapturing)
          .skip(index - 1)
          .first();
    }
static RegExpGroup resolve(int index, PsiFile file)