[ONOS-5625] Null-Provides: Implement the chordal topology

Change-Id: I4142694e2762ecbbfd6f776131d5269e412e86c3
diff --git a/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java b/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java
index 5d65caf..65686a9 100644
--- a/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java
+++ b/providers/null/src/main/java/org/onosproject/provider/nil/NullProviders.java
@@ -367,6 +367,8 @@
             return new GridTopologySimulator();
         } else if (topoShape.matches("fattree([,].*|$)")) {
             return new FatTreeTopologySimulator();
+        } else if (topoShape.matches("chordal([,].*|$)")) {
+            return new ChordalTopologySimulator();
         } else if (topoShape.matches("custom([,].*|$)")) {
             return new CustomTopologySimulator();
         } else {