private @Nullable String getIndentString() {
      if (nodes.size() > 0) {
        ASTNode prev = nodes.get(0).getTreePrev();
        if (prev != null && prev.getPsi() instanceof PsiWhiteSpace && prev.textContains('\n')) {
          CharSequence whitespace = prev.getChars();
          int lineStart = CharArrayUtil.lastIndexOf(whitespace, "\n", whitespace.length() - 1);
          if (lineStart >= 0) {
            return whitespace.subSequence(lineStart + 1, whitespace.length()).toString();
          }
        }
      }
      return null;
    }
private @Nullable String getIndentString()