public virtual void TestKeySetEntrySetAndValues()
 {
     Assert.IsTrue(mm.Put("key1", "value1"));
     Assert.IsTrue(mm.Put("key1", "value2"));
     Assert.IsTrue(mm.Put("key1", "value3"));
     Assert.IsTrue(mm.Put("key2", "value4"));
     Assert.IsTrue(mm.Put("key2", "value5"));
     Assert.AreEqual(2, mm.KeySet().Count);
     Assert.AreEqual(5, mm.Values().Count);
     Assert.AreEqual(5, mm.EntrySet().Count);
 }