code: function getNextChild(child) {
           var index = this.children.indexOf(child) - 1;
  
           if (index >= 0 && index < this.children.length) {
             return this.getChildAt(index);
           }
  
           return undefined;
         }
docs: Returns the next child within the container or undefined if none
  @name getNextChild
  @memberOf me.Container
  @function
  @param {me.Renderable} child