This is a quick hack to draw two parallel links between nodes. Yes, you can scale it to more than two nodes, but it gets increasingly awkward. The alternative is to compute the paths manually, say by computing the perpendicular vector of the vector between the node centers, and offsetting the links accordingly.
forked from mbostock's block: Molecule
forked from anonymous's block: PaisPersonaje
forked from willroj's block: PaisPersonaje2
https://d3js.org/d3.v3.min.js