Improvement: handling multiple links between nodes

Hi, I am looking at:
https://bl.ocks.org/mattkohl/146d301c0fc20d89d85880df537de7b0

at the moment in ngraph is possibile to have two link between two nodes, with an id of the edge like "from.id-to.id" corresponding to the id of vertexes.

Have you considered the possibility to pass custom IDs , so that is possible to have multiple types of links?

Start by reviewing the linked example and the current ngraph behavior for link IDs between the same pair of nodes. Determine how custom IDs would be passed and what multiple link types should look like; done means parallel links can coexist without conflicting IDs.

Written by the indexing model from the issue text.