The reason I did it this way was because the style in this case is an object of objects like this:
```javascript
{
    "nodes": {
        "color": [0, 0, 1]
    },
    "lines": {
        "color": [1, 1, 1]
    }
}
```
So, the semantics of a two argument call is somewhat different than the other style methods in that you can't just call `style("color", [1, 1, 1])`, the second argument needs to be an object.  In this case, the super method does this:
```javascript
m_style[arg1] = arg2;
```
This overwrites the style of `arg1` rather than merging them.  Some extra logic would have to be added to `feature.style` to do `$.extend(m_style[arg1], arg2)` when appropriate.