def METHOD_NAME():
    url = "http://example.org/echo_headers"
    client = httpx.Client(
        transport=httpx.MockTransport(echo_repeated_headers_multi_items)
    )
    response = client.get(url, headers=[("x-header", "1"), ("x-header", "2,3")])
    assert response.status_code == 200
    echoed_headers = response.json()["headers"]
    assert ["x-header", "1"] in echoed_headers
    assert ["x-header", "2,3"] in echoed_headers