docs: def register(self, *actions):
          """Register `actions` in the current application. All `actions` must be
          an instance of :class:`.Action` or one of its subclasses.
  
          If `overwrite` is `True`, then it is allowed to overwrite an
          existing action with same name and category; else `ValueError`
          is raised.
          """
          assert self.installed(), "Actions not enabled on this application"
          assert all(isinstance(a, Action) for a in actions)
  
          for action in actions:
              cat = action.category
              reg = self._state["categories"].setdefault(cat, [])
              reg.append(action)