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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 logout_callback():
 """Route called by the OpenID provider when user logs out. Clear the cookies here. """

    resp = make_response('Logging Out')
    resp.set_cookie('sub', 'null', expires=0)
    resp.set_cookie('session_id', 'null', expires=0)
    return resp