code: def register_namespace(self, namespace, module):
          
          if namespace in self._namespaces:
              raise AlreadyRegisteredError("Namespace '{0}' is already registered on loader.".format(namespace))
  
          self._namespaces[namespace] = module
docs: 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