def register_namespace(self, namespace, module):
if namespace in self._namespaces:<EOL><INDENT>raise AlreadyRegisteredError("<STR_LIT>".format(namespace))<EOL><DEDENT>self._namespaces[namespace] = module<EOL>
Register a namespace.

:param namespace: Namespace tag.
:type namespace: str
:param module: must be a string or a module object to register.
:type module: str