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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 setup_privnet(self, host=None):
 """ Load settings from the privnet JSON config file Args: host (string, optional):
 if supplied, uses this IP or domain as neo nodes. The host must use these standard ports: P2P 20333, RPC 30333. """

        self.setup(FILENAME_SETTINGS_PRIVNET)
        if isinstance(host, str):
            if ":" in host:
                raise Exception("No protocol prefix or port allowed in host, use just the IP or domain.")
            print("Using custom privatenet host:", host)
            self.SEED_LIST = ["%s:20333" % host]
            self.RPC_LIST = ["http://%s:30333" % host]
            print("- P2P:", ", ".join(self.SEED_LIST))
            print("- RPC:", ", ".join(self.RPC_LIST))
        self.check_privatenet()