Adding XML attributes to JUNG GraphML

I'm using JUNG to construct a Graph and then writing out to GraphML using a GraphMLWriter. Using the addVertexData and addEdgeData methods I can get <data> tags output to the XML.

e.g. I can get the following:

<edge id="123" source="456" target="789">
    <data key="firstname">John</data>
</edge>

by adding a Transformer using addEdgeData

Is there a way for me to add XML attributes onto the edge node itself, e.g. to get the following?

<edge id="123" source="456" target="789" label="theDescriptionOfMyEdge">
    <data key="firstname">John</data>
</edge>