Pass code check with pylint=2.4.4 (#1012)

examples/natnet.py

@@ -27,6 +27,7 @@ from mininet.util import irange
 
 class InternetTopo(Topo):
     "Single switch connected to n hosts."
+    # pylint: disable=arguments-differ
     def build(self, n=2, **_kwargs ):
         # set up inet switch
         inetSwitch = self.addSwitch('s0')
@@ -62,6 +63,7 @@ def run():
     CLI(net)
     net.stop()
 
+
 if __name__ == '__main__':
     setLogLevel('info')
     run()