config ang key validation and UT for the same

Change-Id: I507740fc9da3f3da5fb3c88a7414f87db6251c5b
diff --git a/utils/yangutils/src/test/resources/NoConfigContainerSubStatementContainer.yang b/utils/yangutils/src/test/resources/NoConfigContainerSubStatementContainer.yang
new file mode 100644
index 0000000..1aded2d
--- /dev/null
+++ b/utils/yangutils/src/test/resources/NoConfigContainerSubStatementContainer.yang
@@ -0,0 +1,15 @@
+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    container hello {
+        container valid {
+            leaf invalid-interval {
+                type "uint16";
+                units "seconds";
+                status current;
+                reference "RFC 6020";
+            }
+        }
+    }
+}
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