[ONOS-3894, 4071] YANG Advanced Construct Union & Grouping

Change-Id: I0f828adb5884c2d7b6e4120f9843c416608ae5e7
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumerationListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumerationListener.java
index 0dab0f1..87d51b4 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumerationListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumerationListener.java
@@ -45,6 +45,7 @@
 import org.onosproject.yangutils.datamodel.YangLeaf;
 import org.onosproject.yangutils.datamodel.YangLeafList;
 import org.onosproject.yangutils.datamodel.YangType;
+import org.onosproject.yangutils.datamodel.YangUnion;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
@@ -102,7 +103,10 @@
                 case LEAF_LIST_DATA:
                     enumerationNode.setEnumerationName(((YangLeafList) tmpData).getLeafName());
                     break;
-                // TODO typedef, union, deviate.
+                case UNION_DATA:
+                    enumerationNode.setEnumerationName(((YangUnion) tmpData).getUnionName());
+                    break;
+                // TODO typedef, deviate.
                 default:
                     throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, TYPE_DATA,
                             ((YangType<?>) typeData).getDataTypeName(), ENTRY));