How to use the blacksheep.Headers function in blacksheep

def test_http_header_collection_concatenation_with_other_collection():
    headers = Headers([
        (b'Hello', b'World'),
        (b'Svil', b'Power'),
    ])

    with_addition = headers + Headers([(b'Foo', b'foo'), (b'Ufo', b'ufo')])

    for name in {b'foo', b'ufo'}:
        assert headers[name] == tuple()

        example = with_addition[name]
        assert len(example) == 1

        header = example[0]
        assert header == name

def test_iadd_http_header_collection_concatenation_with_collection_of_headers():
    headers = Headers([
        (b'Hello', b'World'),
        (b'Svil', b'Power'),
    ])

    headers += Headers([(b'foo', b'foo'), (b'ufo', b'ufo')])

    for name in {b'foo', b'ufo'}:
        example = headers[name]
        assert len(example) == 1

        header = example[0]
        assert header == name

def test_iadd_http_header_collection_concatenation_with_collection_of_headers():
    headers = Headers([
        (b'Hello', b'World'),
        (b'Svil', b'Power'),
    ])

    headers += Headers([(b'foo', b'foo'), (b'ufo', b'ufo')])

    for name in {b'foo', b'ufo'}:
        example = headers[name]
        assert len(example) == 1

        header = example[0]
        assert header == name

def test_http_header_collection_instantiating_with_list_of_tuples(values):
    headers = Headers(values)

    for input_header in values:
        header = headers[input_header[0]]
        assert len(header) == 1
        assert header[0] == input_header[1]

def test_http_header_collection_item_getter_case_insensitive():
    headers = Headers()
    headers[b'example'] = b'Hello, World'

    header = headers[b'Example']
    assert header == (b'Hello, World',)

def test_iadd_http_header_collection_concatenation_with_duplicate_():
    headers = Headers([
        (b'Hello', b'World'),
        (b'Svil', b'Power'),
    ])

    headers += (b'Svil', b'Kitty')
    example = headers[b'Svil']

    assert len(example) == 2
    assert any(x == b'Power' for x in example)
    assert any(x == b'Kitty' for x in example)

def test_http_header_collection_instantiating_with_list_of_headers_repeated_values(values):
    headers = Headers(values)

    for input_header in values:
        input_headers_with_same_name = [x[1] for x in values if x[0] == input_header[0]]

        header = headers[input_header[0]]
        assert len(header) == len(input_headers_with_same_name)
        assert any(x == y for x in header for y in input_headers_with_same_name)

def test_http_header_collection_add_many_items():
    headers = Headers()

    values = {
        b'A': b'B',
        b'C': b'D',
        b'E': b'F',
    }

    headers.add_many(values)

    for key, value in values.items():
        header = headers.get_single(key)
        assert header is not None
        assert header == value

async def frozen_file_getter(request):
        previous_etag = request.if_none_match

        if previous_etag and previous_etag == current_etag:
            return Response(304, headers, None)

        if request.method == 'HEAD':
            return Response(200, head_headers, None)

        return Response(200, Headers(headers), Content(mime, data))
    return frozen_file_getter