code: public static One<String> ofString(String msg, Object... args) {
      return One.of(Helper.parse(msg, args));
    }
docs: Creates a One of String based on the given message. The message can be a
  slf4j string with {} placeholders that will be replaced by the given
  optional arguments.
  
  @param msg
  the message string with possible placeholders
  @param args
  the values to replace the placeholders with
  @return a One