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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 main(pub_port=None, sub_port=None):
    '''main of forwarder

    :param sub_port: port for subscribers
    :param pub_port: port for publishers
    '''
    try:
        if sub_port is None:
            sub_port = get_sub_port()
        if pub_port is None:
            pub_port = get_pub_port()
        context = zmq.Context(1)
        frontend = context.socket(zmq.SUB)
        backend = context.socket(zmq.PUB)

        frontend.bind('tcp://*:{pub_port}'.format(pub_port=pub_port))
        frontend.setsockopt(zmq.SUBSCRIBE, b'')
        backend.bind('tcp://*:{sub_port}'.format(sub_port=sub_port))
        zmq.device(zmq.FORWARDER, frontend, backend)
    except KeyboardInterrupt:
        pass
    finally:
        frontend.close()
        backend.close()
        context.term()