code: function downgradeNodesInternal(nodes) {
      /**
       * Auxiliary function to downgrade a single node.
       * @param  {!Node} node the node to be downgraded
       */
      var downgradeNode = function(node) {
        createdComponents_.filter(function(item) {
          return item.element_ === node;
        }).forEach(deconstructComponentInternal);
      };
      if (nodes instanceof Array || nodes instanceof NodeList) {
        for (var n = 0; n < nodes.length; n++) {
          downgradeNode(nodes[n]);
        }
      } else if (nodes instanceof Node) {
        downgradeNode(nodes);
      } else {
        throw new Error('Invalid argument provided to downgrade MDL nodes.');
      }
    }
docs: Downgrade either a given node, an array of nodes, or a NodeList.
  
  @param {!Node|!Array<!Node>|!NodeList} nodes