code: function ( index ) {
  
              var shape = this.pointShapes[ index ],
              // 当前的包含的数据点
                  vertex = this.points[ index ].getVertex();
  
              shape.line.setPoint1( vertex.x, vertex.y ).setPoint2( vertex.x, vertex.y );
              shape.forward.setCenter( vertex.x, vertex.y );
              shape.backward.setCenter( vertex.x, vertex.y );
  
              this._stroke( shape.vertex, "white" );
  
          }
docs: 清理指定索引的图形点, 使得该点仅显示一个顶点