private static void TestIteratorEntryReadOnly(IHttp2Headers headers)
        {
            var enumerator = headers.GetEnumerator();

            Assert.True(enumerator.MoveNext());
            enumerator.Current.SetValue((AsciiString)"foo");
        }
        private static void TestIteratorReadOnly(IHttp2Headers headers)
        {
            var enumerator = headers.GetEnumerator();

            Assert.True(enumerator.MoveNext());
            headers.Remove(enumerator.Current.Key);
        }