                    tooltip: {
                        trigger: 'item'
                    },
                    series:[
                        {
                            type: 'tree',
                            data: [{
                                name: 'root'
                            }],
                            top: '18%',
                            bottom: '14%',
                            roam: true,
                            layout: 'radial',
                            symbol: 'e