public List<String> getAll(String headerName) {
        String normalName = HeaderName.normalize(Objects.requireNonNull(headerName, "headerName"));
        return getAllNormal(normalName);
    }
@Test
    void getAll() {
        Headers headers = new Headers();
        headers.add("Via", "duct");
        headers.add("Cookie", "this=that");
        headers.add("Cookie", "frizzle=frazzle");

        Truth.assertThat(headers.getAll("CookiE"))
                .containsExactly("this=that", "frizzle=frazzle")
                .inOrder();
    }