`findParentBy` - determines the way how a cell finds a suitable parent when it's dragged over the paper. The cell with the highest z-index (visually on the top) will be chosen. `findParentBy` option comes to play when the paper is in embedding mode. All possible values are `'bbox'` (default), `'center'`, `'origin'`, `'corner'`, `'topRight'`, `'bottomLeft'` and it also can be a `function`. The function accepts an `element` and it returns array of possible candidates.

    findParentBy: function(element) {
        var bBox = element.getBBox();
        return this.getElements().filter(function(el) {
            return bBox.intersect(el.getBBox());
        });
    }