public void TryGetByValueTest()
        {
            var bi = new BiDirectionalDictionary <int, int> {
                { 1, 10 }, { 2, 20 }, { 3, 30 }
            };

            Assert.IsTrue(bi.TryGetByValue(10, out var key));
            Assert.AreEqual(1, key);
            Assert.IsFalse(bi.TryGetByValue(100, out _));
        }
        public void BiDirectionalDictionaryTryGetByValue()

        {
            var bi = new BiDirectionalDictionary <int, int> {
                { 1, 1 }, { 2, 12 }
            };

            Assert.AreEqual(2, bi.Count);
            var found = bi.TryGetByValue(12, out var key);

            Assert.IsTrue(found);
            Assert.AreEqual(2, key);
        }