public void TryGetValueTest()
        {
            GraphCompositeBuilder<int, string> gcb = new GraphCompositeBuilder<int, string>(EqualityComparer<int>.Default, 0, "root");
            gcb.AddNode(0, 1, "subG", true);
            string value = null;

            Assert.AreEqual(gcb.TryGetValue(0, out value), true);
            Assert.AreEqual(value, "root");
            Assert.AreEqual(gcb.TryGetValue(1, out value), true);
            Assert.AreEqual(value, "subG");
            value = null;
            Assert.AreEqual(gcb.TryGetValue(2, out value), false);
            Assert.IsNull(value);
        }