code: function(nodes) {
          var ans = [], config = this.config, root = this.viz.root;
          nodes.sort(function(a, b) { return (a._depth <= b._depth) - (a._depth >= b._depth); });
          for(var i=0; i<nodes.length; i++) {
              if(nodes[i].anySubnode("exist")) {
              	for (var j = i+1, desc = false; !desc && j < nodes.length; j++) {
                      if(!config.multitree || '$orn' in nodes[j].data) {
                  		desc = desc || nodes[i].isDescendantOf(nodes[j].id);                    	
                      }
                  }
                  if(!desc) ans.push(nodes[i]);
              }
          }
          return ans;
      }
docs: /*
  Filters an array of nodes leaving only nodes with children.