Convenience operation to help walking JSON structures.
diff --git a/jena-arq/src/main/java/org/apache/jena/atlas/json/JsonObject.java b/jena-arq/src/main/java/org/apache/jena/atlas/json/JsonObject.java
index b83d1cb..b7e89db 100644
--- a/jena-arq/src/main/java/org/apache/jena/atlas/json/JsonObject.java
+++ b/jena-arq/src/main/java/org/apache/jena/atlas/json/JsonObject.java
@@ -54,11 +54,6 @@
         return map.containsKey(key) ;
     }
     
-//    @Override
-//    public boolean containsValue(Object value) {
-//        return map.containsValue(value) ;
-//    }
-    
     public Set<String> keys() {
         return map.keySet() ;
     }
@@ -71,6 +66,11 @@
         return map.get(key) ;
     }
 
+    /** For walking structures */
+    public JsonObject getObj(String key) {
+        return get(key).getAsObject() ;
+    }
+
     public boolean isEmpty() {
         return map.isEmpty() ;
     }