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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 runserver(host=None, port=None):
 """ Run Tornado server """

    host = host or os.getenv('HTTP_HOST', '0.0.0.0')
    port = port or os.getenv('HTTP_PORT', '9001')
    zioloop = ioloop.IOLoop.instance()

    # setup pika client:
    pc = QueueManager(zioloop)
    app.pc = pc
    pc.connect()
    app.listen(port, host)
    zioloop.start()