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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 run(host='127.0.0.1', port=8000):
 """ Run web server. """

    print("Server running on {}:{}".format(host, port))
    app_router = Router()
    server = make_server(host, port, app_router)
    server.serve_forever()