code: private void appendSeparator() {
      if (separators.length() == 1) {
        appendNormal(separators.charAt(0));
      } else {
        builder.append('[');
        for (int i = 0; i < separators.length(); i++) {
          appendInBracket(separators.charAt(i));
        }
        builder.append("]");
      }
    }
docs: Appends the regex form matching the separators for the path type.