What is the ongoing bipartite graph support?

I found a PR to support bipartite graph, instead of the direction of the message, what is the difference from a normal graph?

A bipartite graph is a special case of heterograph. It has two groups of nodes and each group can have different feature data scheme (e.g, different feature sizes, different feature names, etc.). Thus, bipartite graph also has different node id space than normal graph. For example, in normal graph, we assign consecutive integer ids to nodes (0, 1, 2, …), while in bipartite graph, the id space should be isolated so their feature data can be stored separately. These make us feel that bipartite graph needs quite different implementation and we are currently working on it.

Yeah, these seems great, by the way, is there any reference documentation, or something like this?