code: public void extendWith(Namespace ns) {
  	if (ns==null) return;
  	if (ns.getDefaultNamespace()!=null) {
  	    registerDefault(ns.getDefaultNamespace());
  	}
  	for (String prefix: ns.prefixes.keySet()) {
  	    register(prefix, ns.prefixes.get(prefix));
  	}
      }
docs: Extends this Namespace with all the prefix/namespace registration of the Namespace received as argument.
  @param ns the {@link Namespace} whose prefix/namespace registration are added to this {@link Namespace}.