docs: def unregister(self, event):
          """
          Remove all registered handlers for an event.
          Silent return when event was not registered.
  
          Usage:
  
              dispatch.unregister("my_event")
              dispatch.unregister("my_event")  # no-op
  
          """
          if self.running:
              raise RuntimeError("Can't unregister while running")
          self._handlers.pop(event, None)