def prefix_key_with_namespace(key, ns_index = nil)
      namespace = (ns_index.nil?) ? DEFAULT_NAMESPACE : ("ns%d" % ns_index)
      return prefix_key(key, namespace)
    end
def prefix_key_with_namespace(key, ns_index = nil)
      namespace = (ns_index.nil?) ? DEFAULT_NAMESPACE : ("ns%d" % ns_index)
      return prefix_key(key, namespace)
    end
Prefixes a key with a given namespace index or default namespace.