public void Demonstrate_DbReference()
        {
            var session = new MongoSession();

            var supplier = new Supplier { Name = "Acme" };
            session.Save(supplier);

            var product = new Product {
                Name = "Shovel",
                Price = "17.50",
                Sku = "a3k4j22je9",
                Weight = "11",
                Supplier = new DbReference<Supplier>(supplier.Id)
            };
            session.Save(product);

            var fetched = session.Query<Product>().Where(x => x.Sku == product.Sku);

            Assert.AreEqual(fetched.First().Supplier.Id, supplier.Id);

            var fetchedSupplier = fetched.First().Supplier.Fetch(() => session.GetDb());

            Assert.AreEqual(fetchedSupplier.Name, supplier.Name);
        }