private static TestGraph DeserializeGraph([NotNull] string xml)
 {
     using (var reader = new StringReader(xml))
     {
         var serializedGraph = new TestGraph();
         serializedGraph.DeserializeAndValidateFromGraphML(
             reader,
             id => new TestVertex(id),
             (source, target, id) => new TestEdge(source, target, id));
         return(serializedGraph);
     }
 }