NormalizeData sorts data and performs other postprocessing.

PopulateImpliedFields fills in fields on graph data objects that individual toolchains leave blank but that are implied by the source unit the graph data objects were built from.

Register sets the grapher to be used for source units of the given type.

UnresolvedInternalRefs returns a map of unresolved internal refs, keyed on the (nonexistent) defs they point to.

Graphers holds all registered graphers.