code: function(requested, optimized, callback) {
          // uses the length tree complement calculator.
          var self = this;
          var complementResult = complement(requested, optimized, self._pathMap);
  
          var inserted = false;
          var disposable = false;
  
          // If we found an intersection, then just add new callback
          // as one of the dependents of that request
          if (complementResult.intersection.length) {
              inserted = true;
              var idx = self._callbacks.length;
              self._callbacks[idx] = callback;
              self._requestedPaths[idx] = complementResult.intersection;
              self._optimizedPaths[idx] = [];
              ++self._count;
  
              disposable = createDisposable(self, idx);
          }
  
          return [inserted, complementResult.requestedComplement, complementResult.optimizedComplement, disposable];
      }
docs: Attempts to add paths to the outgoing request.  If there are added
  paths then the request callback will be added to the callback list.
  Handles adding partial paths as well
  
  @returns {Array} - whether new requested paths were inserted in this
  request, the remaining paths that could not be added,
  and disposable for the inserted requested paths.