@Nullable
    private static String get(Http2Headers headers, CharSequence name) {
        final CharSequence value = headers.get(name);
        return value != null ? value.toString() : null;
    }
This test is to check the behavior of the HttpClient when the 'Expect: 100-continue' header is set.
core/src/test/java/com/linecorp/armeria/client/HttpClientExpect100HeaderTest.java