Replaced example topologies __init__ with build

custom/topo-2sw-2host.py

@@ -13,12 +13,9 @@ from mininet.topo import Topo
 class MyTopo( Topo ):
     "Simple topology example."
 
-    def __init__( self ):
+    def build( self ):
         "Create custom topo."
 
-        # Initialize topology
-        Topo.__init__( self )
-
         # Add hosts and switches
         leftHost = self.addHost( 'h1' )
         rightHost = self.addHost( 'h2' )