def METHOD_NAME(self) -> None:
    with RequestMockWithProxySupport() as mock_requests:
        mock_requests.add(responses.GET, "http://localhost:4242/")
        OutgoingSession(role="testing", timeout=1, headers={"X-Foo": "bar"}).get(
            "http://example.com/"
        )
        self.assert_length(mock_requests.calls, 1)
        headers = mock_requests.calls[0].request.headers
        self.assertEqual(headers["X-Smokescreen-Role"], "testing")
        # We don't see the request-level headers in the proxy
        # request.  This isn't a _true_ test because we're
        # fiddling the headers above, instead of urllib3 actually
        # setting them.
        self.assertFalse("X-Foo" in headers)