code: void insert(Suffix<T, S> suffix, ActivePoint<T, S> activePoint) {
          Object item = suffix.getEndItem();
          Object nextItem = getItemAt(activePoint.getLength());
          if (item.equals(nextItem)) {
              activePoint.incrementLength();
          } else {
              split(suffix, activePoint);
              suffix.decrement();
              activePoint.updateAfterInsert(suffix);
  
              if (suffix.isEmpty()) {
              }
              else
                  tree.insert(suffix);
          }
      }
docs: Insert the given suffix at the supplied active point.
  
  @param suffix      The suffix to insert.
  @param activePoint The active point to insert it at.
  @return