minus(duration) {
    if (!this.isValid) return this;

    const dur = Duration.fromDurationLike(duration);
    return this.plus(dur.negate());
  }
Make this Duration shorter by the specified amount. Return a newly-constructed Duration.
@param {Duration|Object|number} duration - The amount to subtract. Either a Luxon Duration, a number of milliseconds, the object argument to Duration.fromObject()
@return {Duration}