code: function(elementA, elementB) {
  
          var isSuccessor = false;
          this.search(elementA, function(element) {
              if (element === elementB && element !== elementA) {
                  isSuccessor = true;
                  return false;
              }
          }, { outbound: true });
          return isSuccessor;
      }
docs: Return `true` is `elementB` is a successor of `elementA`. Return `false` otherwise.