will remove a namespace ref from the manager. either Arg is
        optional.

        args:
            namespace: prefix, string or Namespace() to remove

def del_ns(self, namespace):
        """ will remove a namespace ref from the manager. either Arg is
        optional.

        args:
            namespace: prefix, string or Namespace() to remove
        """
        # remove the item from the namespace dict
        namespace = str(namespace)
        attr_name = None
        if hasattr(self, namespace):
            delattr(self, namespace)