DiffGraph

A lightweight write-only graph used for creation of CPG graph overlays

The graph can store edges to/from nodes that do not exist in the base graph. It doesn't assign ids for these nodes until the diff graph is serialized. Ids of new nodes may collide with ids of nodes in the base graph, which are not sources or destinations of edges of the diff graph. When the CPG loader adds nodes of the overlay, it therefor needs to reassign ids for nodes if they are already used in the original CPG.