code: function(newNode, referenceNode) {
              newNode = Y.Dom.get(newNode); 
              referenceNode = Y.Dom.get(referenceNode); 
              
              if (!newNode || !referenceNode || !referenceNode[PARENT_NODE]) {
                  return null;
              }       
  
              return referenceNode[PARENT_NODE].insertBefore(newNode, referenceNode); 
          }
docs: Inserts the new node as the previous sibling of the reference node
  @method insertBefore
  @param {String | HTMLElement} newNode The node to be inserted
  @param {String | HTMLElement} referenceNode The node to insert the new node before
  @return {HTMLElement} The node that was inserted (or null if insert fails)