docs: function (dragElement) {
              // get dropzones and their elements that could receive the draggable
              var possibleDrops = this.collectDrops(dragElement, true);
  
              this.activeDrops.dropzones = possibleDrops.dropzones;
              this.activeDrops.elements  = possibleDrops.elements;
              this.activeDrops.rects     = [];
  
              for (var i = 0; i < this.activeDrops.dropzones.length; i++) {
                  this.activeDrops.rects[i] = this.activeDrops.dropzones[i].getRect(this.activeDrops.elements[i]);
              }
          }