def get_cookie_header(jar, request):
    """
    Produce an appropriate Cookie header string to be sent with `request`, or None.

    :rtype: str
    """
    r = MockRequest(request)
    jar.add_cookie_header(r)
    return r.get_new_headers().get('Cookie')

    Produce an appropriate Cookie header string to be sent with `request`, or None.

    :rtype: str
    
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_vendor/requests/cookies.py