docs: public TimeSlot insertSlotAtEnd(long newSlotTimeout) {
          // this routine assumes that list could be empty
          TimeSlot retSlot = new TimeSlot(newSlotTimeout);
          if (this.lastSlot == null) {
              // list was empty
              this.lastSlot = retSlot;
              this.firstSlot = retSlot;
          } else {
              retSlot.prevEntry = this.lastSlot;
              this.lastSlot.nextEntry = retSlot;
              this.lastSlot = retSlot;
          }
          return retSlot;
      }