code: function(item){
      var children,node, nodes;
      if(!item) return;
      if(typeof item.node === "function") return item.node();
      if(typeof item.nodeType === "number") return item;
      if(item.group) return combine.node(item.group)
  
      item = item.children || item;
      if( Array.isArray(item )){
        var len = item.length;
        if(len === 1){
          return combine.node(item[0]);
        }
        nodes = [];
        for(var i = 0, len = item.length; i < len; i++ ){
          node = combine.node(item[i]);
          if(Array.isArray(node)){
            for (var j = 0, len1 = node.length; j < len1; j++){
              nodes.push(node[j])
            }
          }else if(node) {
            nodes.push(node)
          }
        }
        return nodes;
      }
      
    }
docs: get the initial dom in object