private static void ExpandGraphs(this ITripleStore store, TripleStore targetStore, Uri metaGraphUri)
        {
            IGraph metaGraph = store.AddGraph(metaGraphUri);

            foreach (Triple triple in targetStore.Triples)
            {
                IUriNode subject = (triple.Subject is IBlankNode ? targetStore.FindOwningSubject((IBlankNode)triple.Subject) : (IUriNode)triple.Subject);
                if (subject != null)
                {
                    IGraph graph = store.GetGraph(metaGraphUri, subject.Uri);
                    graph.Assert(graph.Import(triple));
                }
            }
        }