@type t() ::
  ((((((((((((((((((((((((:join_start | :node_changes) | :user_changes)
                        | :join_end)
                       | :signal)
                      | :style)
                     | :style_set)
                    | :join_start_skip_reload)
                   | :notify_should_upgrade)
                  | :upgrade_done)
                 | :upgrade_refresh)
                | :scene_graph_query)
               | :scene_graph_reply)
              | :diff)
             | :client_broadcast)
            | :join_start_journaled)
           | :stream_start)
          | :stream_end)
         | :interactive_slide_change)
        | :reconnect_scene_graph_query)
       | :reconnect_scene_graph_reply)
      | :join_end_incremental_reconnect)
     | :node_status_change)
    | :client_rendered)
   | :buzz_approval_change)
  | integer()