docs: def add_namespace(self, namespace, interface=None, check_extras=True,
                        load_now=False):
          """
          register given namespace in global database of plugins
  
          in case it's already registered, return the registration
          """
          tempo = self._namespaces.get(namespace)
  
          if tempo is None:
              tempo = _Plugins(namespace, interface, check_extras)
              self._namespaces[namespace] = tempo
  
          if load_now:
              tempo.load()
  
          return tempo