human
Solve the following python programming problem given the following code:
def main() : 
    parser = argparse.ArgumentParser (description = 'Launch a dht node which responds to rpc commands') 
    parser.add_argument ('node_port', help = 'The UDP port on which the node will listen for connections from other dht nodes', type = int) 
    parser.add_argument ('rpc_port', help = 'The TCP port on which the node will listen for rpc commands', type = int) 
    parser.add_argument ('dht_bootstrap_host', help = 'The IP of a DHT node to be used to bootstrap into the network', nargs = '?') 
    parser.add_argument ('dht_bootstrap_port', help = 'The port of a DHT node to be used to bootstrap into the network', nargs = '?', default = 4000, type = int) 
    parser.add_argument ('--rpc_ip_address', help = 'The network interface on which to listen for rpc connections', default = '127.0.0.1') 
    args = parser.parse_args () 
    def start_rpc() : 
        rpc_node = RPCNode (node, shut_down) 
        reactor.listenTCP (args.rpc_port, server.Site (rpc_node), interface = args.rpc_ip_address) 
def shut_down() : 
        d = defer.maybeDeferred (node.stop) 
        d.addBoth ((lambda _ : reactor.stop ())) 
        return d 
known_nodes = [] 
    if args.dht_bootstrap_host : 
        known_nodes.append ((args.dht_bootstrap_host, d.dht_bootstrap_port)) 
node = Node (udpPort = args.node_port) 
    node.joinNetwork (known_nodes) 
    d = node._joinDeferred 
    d.addCallback ((lambda _ : start_rpc ())) 
    reactor.run () 

    
    

    Fix the buggy line: known_nodes.append ((args.dht_bootstrap_host, d.dht_bootstrap_port))
assistant
#Here is Python program to fix the buggy line: known_nodes.

known_nodes.append ((args.dht_bootstrap_host, args.dht_bootstrap_port))