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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 base_ws_uri():
 """Base websocket URL that is advertised to external clients. Useful when the websocket URL advertised to the clients needs to be customized (typically when running behind NAT, firewall, etc.) """


    scheme = config['wsserver']['advertised_scheme']
    host = config['wsserver']['advertised_host']
    port = config['wsserver']['advertised_port']
    return '{}://{}:{}'.format(scheme, host, port)