code: function _initTransferableAnimations(item, prevItem, callback) {
          var callbackCount = 0;
          function waitForAll() {
              callbackCount--;
              if (callbackCount === 0) {
                  callback();
              }
          }
          for (var sourceId in item.options.transfer.items) {
              if (_initTransferableAnimation.call(this, item, prevItem, sourceId, waitForAll)) {
                  callbackCount++;
              }
          }
          if (!callbackCount) {
              callback();
          }
      }
docs: Begins visual transfer or renderables from the previous item
  to the new item.