docs: public static String format(String pattern, Object... args) {
  
      if (args == null)
        return pattern;
  
      StringBuilder str = new StringBuilder(pattern.length() + 50);
      int idx = -1;
      int i = 0;
      int p = 0;
      while ((idx = pattern.indexOf(PLACEHOLDER, p)) != -1) {
        str.append(pattern.substring(p, idx));
        Object arg = args[i];
        if (arg == null) {
          str.append(JsonWriter.CONST_NULL);
        } else {
          str.append(args[i].toString());
        }
        i++;
        p = idx + 1;
      }
      str.append(pattern.substring(p));
      return str.toString();
    }