Python 自定义拓扑迷你网

我正在开发一个项目，在这个项目中，我必须创建一个圆形拓扑，但是当我运行拓扑时，这会给我一个错误

 from mininet.net import Mininet
    from mininet.node import OVSSwitch, Controller
    from mininet.topo import Topo
    from mininet.log import setLogLevel
    from mininet.cli import CLI
    
    setLogLevel( 'info' )
    
    # Two remote controllers
    c1 = Controller( 'c1', port=6634 )
    c2 = Controller( 'c2', port=6633 )
    
    # You dont need the links between the controller and the switches,
    # You can connect with the personalized mapping
    cmap = { 's1': c1, 's2': c1, 's3': c2 , 's4': c2}
    class NatTopo( Topo ):
        def build( self, natIP='10.0.0.254' ):
            self.hopts = { 'defaultRoute': 'via ' + natIP }
            hosts = [ self.addHost( h ) for h in 'h1', 'h2', 'h3', 'h4' ]
            s1 = self.addSwitch( 's1' )
            s2 = self.addSwitch( 's2' )
            s3 = self.addSwitch( 's3' )
            s4 = self.addSwitch( 's4' )
            for h in hosts:
                self.addLink( s1, h )
                self.addLink( s2, h )
                self.addLink( s3, h )
                self.addLink( s4, h )
            nat1 = self.addNode( 'nat1', cls=NAT, ip=natIP,
                                 inNamespace=False )
            self.addLink( nat1, s1 )
            self.addLink( nat1, s2 )
            self.addLink( nat1, s3 )
             self.addLink( nat1, s4 )
class MultiSwitch( OVSSwitch ):
    "Custom Switch() subclass that connects to different controllers"
    def start( self, controllers ):
        return OVSSwitch.start( self, [ cmap[ self.name ] ] )

class MyTopo(Topo):

 def __init__( self ):
        "Create custom topo."



topo = MyTopo()
net = Mininet( topo=topo, switch=MultiSwitch, build=False )
net.addNAT().configDefault()
for c in [ c1, c2 ]:
    net.addController(c)
net.build()
net.start()
CLI( net )
net.stop()
topos = { 'mytopo': ( lambda: MyTopo() ) }

当我尝试启动拓扑时，出现以下错误：

mininet@mininet-vm:~/mininet/custom$ sudo python custom-topo-proj.py
Traceback (most recent call last):
  File "custom-topo-proj.py", line 60, in <module>
    net.addNAT().configDefault()
  File "build/bdist.linux-x86_64/egg/mininet/net.py", line 282, in addNAT

mininet@mininet-vm:~/mininet/custom$sudo python custom-topo-proj.py
回溯（最近一次呼叫最后一次）：
文件“custom topo proj.py”，第60行，输入
net.addNAT（）.configDefault（）
addNAT中第282行的文件“build/bdist.linux-x86_64/egg/mininet/net.py”

索引器：列表索引超出范围

如果有人帮我解决这个问题，我会启动nat并连接所有链接