code: function (priority) {
              var retVal;
              if (sjl.classOfIs(priority, Number)) {
                  retVal = priority;
              }
              else {
                  this._internalPriorities += 1;
                  retVal = +this._internalPriorities;
              }
              return retVal;
          }
docs: Ensures priority returned is a number or increments it's internal priority counter
  and returns it.
  @param priority {Number}
  @method sjl.stdlib.PriorityList#normalizePriority
  @returns {Number}