[graph-tool] close edges

Hello, I'm trying to find a way to spatially separate edges from each other in cases where two nodes are connected by many edges. This is done by default but I'd like them to be even more spread out so that I can put readable text on each edge. I've a feeling this can be accomplished by edge_control_points but can't figure out how to specify appropriate bézier control points. Any hints would be greatly appreciated ! Best, -bertrand