private static Pair<String, PsiElement> collectWhitespace(PsiElement start) {
    StringBuilder sb = new StringBuilder();
    PsiElement seeker = start;
    while (seeker != null) {
      seeker = seeker.getNextSibling();
      if (seeker instanceof PsiWhiteSpace) sb.append(seeker.getText());
      else break;
    }
    return Pair.create(sb.toString(), seeker);
  }
private static Pair<String, PsiElement> collectWhitespace(PsiElement start)