code: function moveUp(child) {
           var childIndex = this.getChildIndex(child);
  
           if (childIndex - 1 >= 0) {
             // note : we use an inverted loop
             this.swapChildren(child, this.getChildAt(childIndex - 1));
           }
         }
docs: Move the child in the group one step forward (z depth).
  @name moveUp
  @memberOf me.Container.prototype
  @function
  @param {me.Renderable} child