docs: private void leftAdd(
                          GBSNode           p,
                          GBSNode           r,
                          Object            new1,
                          NodeInsertPoint   ip,
                          InsertNodes       point)
      {
          if (r == null)                 /* There is no upper predecessor         */
              leftAddNoPredecessor(p, new1, ip, point);
          else                           /* There is an upper predecessor         */
              leftAddWithPredecessor(p, r, new1, ip, point);
      }