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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 deauthorize_application(request):
 """ When a user deauthorizes an application, Facebook sends a HTTP POST request to the application's "deauthorization callback" URL. This view picks up on requests of this sort and marks the corresponding users as unauthorized. """

    if request.facebook:
        user = User.objects.get(
            facebook_id = request.facebook.signed_request.user.id
        )

        user.authorized = False
        user.save()

        return HttpResponse()
    else:
        return HttpResponse(status=400)