Add SerializeGraph(..) - for serializing a single graph

There’s currently functionality to load graphs additive and to remove single graphs, all that is missing to be able to fully manage graphs dynamically at runtime is a way to serialize a single graph. Currently only SerializeGraphs(), for all graphs together, is exposed/available. The single graph case would not even need to complicate existing code, just internally create an array from a single graph that is passed as parameter and execute like the already existing method.