## Data Definition


#### Label
Type: `string`

Default validate:  
```js
function (d) { return this.accessor(d) !== "undefined";}
```

Default accessor:  
```js
function (line) { return String(line[0]); }
```

#### Value
Type: `string`

Default validate:  
```js
function (d) { return this.accessor(d) !== "undefined";}
```

Default accessor:  
```js
function (line) { return String(line[1]); }
```