code: public final StandardSubjectBuilder withMessage(
        @NullableDecl String format, Object /* @NullableDeclType */... args) {
      return new StandardSubjectBuilder(metadata().withMessage(format, args));
    }
docs: Returns a new instance that will output the given message before the main failure message. If
  this method is called multiple times, the messages will appear in the order that they were
  specified.
  
  <p><b>Note:</b> the arguments will be substituted into the format template using {@link
  com.google.common.base.Strings#lenientFormat Strings.lenientFormat}. Note this only supports
  the {@code %s} specifier.
  
  @throws IllegalArgumentException if the number of placeholders in the format string does not
  equal the number of given arguments