Port event for NetworkGraphDiscoveryInterface

Change-Id: Iea1e0e5dce4d0f77422573ce4f9154431fb28923
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
index 34e8d51..9dd3877 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
@@ -90,6 +90,7 @@
 			putPort(portEvent);
 			// TODO send out notification
 		}
+		// TODO handle invariant violation
 	}
 
 	@Override
@@ -99,6 +100,7 @@
 			removePort(portEvent);
 			// TODO send out notification
 		}
+		// TODO handle invariant violation
 	}
 
 	@Override