public Lesson(DropInformation dropInformation)
 {
     if (dropInformation.Ndindex == -1)
     {
         dropInfoTwo = dropInformation.Copy();
     }
     else
     {
         dropInfo = dropInformation.Copy();
     }
 }
 public Lesson(PairInfo pairinfo, DropInformation dropInformation) : this(dropInformation)
 {
     pairInfo = pairinfo;
 }
 public Lesson(PairInfo pi, DropInformation dropInfo, DropInformation dropInfoTwo)
 {
     pairInfo         = new PairInfo(pi.Pair, pi.Day);
     this.dropInfo    = dropInfo?.Copy();
     this.dropInfoTwo = dropInfoTwo?.Copy();
 }