[ONOS-4753] Identity/identityref implementation and UT

Change-Id: I40148fa228465555be3bdf410cc294ffc0f34c18
diff --git a/plugin/src/test/resources/IdentityListener.yang b/plugin/src/test/resources/IdentityListener.yang
new file mode 100644
index 0000000..a7ef4d2
--- /dev/null
+++ b/plugin/src/test/resources/IdentityListener.yang
@@ -0,0 +1,39 @@
+module IdentityListener{
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix IdentityListener;
+
+    identity tunnel {
+        description
+           "Base identity from which specific tunnel types are derived.";
+    }
+
+    identity tunnel-type {
+        description
+           "Base identity from which specific tunnel types are derived.";
+    }
+
+    identity ref-address-family {
+        reference "http://www.iana.org/assignments/address-family-numbers/address-family-numbers.xhtml#address-family-numbers-2";
+    }
+
+    identity ipv4-address-family {
+        base ref-address-family;
+    }
+
+    identity ipv6-address-family {
+        base ref-address-family;
+    }
+
+    leaf tunnel {
+        type identityref {
+            base ref-address-family;
+        }
+    }
+
+    leaf-list network-ref {
+        type identityref {
+            base ref-address-family;
+        }
+    }
+}
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