public void GradeCard(ReviewQuality reviewQuality)
 {
     if (reviewQuality.IsWorseThan(ReviewQuality.Difficult))
     {
     }
 }
 public static bool IsWorseThan(this ReviewQuality reviewQuality, ReviewQuality otherReviewQuality)
 {
     return((int)reviewQuality < (int)otherReviewQuality);
 }