How to use the @serenity-js/assertions.ExpectationNotMet function in @serenity-js/assertions

promiseOf(this.fn(actual)).then(_ => _
                ? new ExpectationMet(this.toString(), null, actual)
                : new ExpectationNotMet(this.toString(), null, actual),
            );

and(...this.expectations).answeredBy(actor)(actual).then(_ => _ instanceof ExpectationMet
                ? new ExpectationMet(this.message, _.expected, _.actual)
                : new ExpectationNotMet(_.message, _.expected, _.actual));
    }