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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def view_404(request, url=None):
 """ It returns a 404 http response """

    res = render_to_response("404.html", {"PAGE_URL": request.get_full_path()},
                             context_instance=RequestContext(request))
    res.status_code = 404
    return res