@type t() ::
  (((((((((((((((((((((((((((((:square | :ellipse) | :diamond) | :triangle_up)
                            | :triangle_down)
                           | :rounded_rectangle)
                          | :parallelogram_right)
                         | :parallelogram_left)
                        | :eng_database)
                       | :eng_queue)
                      | :eng_file)
                     | :eng_folder)
                    | :trapezoid)
                   | :predefined_process)
                  | :shield)
                 | :document_single)
                | :document_multiple)
               | :manual_input)
              | :hexagon)
             | :chevron)
            | :pentagon)
           | :octagon)
          | :star)
         | :plus)
        | :arrow_left)
       | :arrow_right)
      | :summing_junction)
     | :or)
    | :speech_bubble)
   | :internal_storage)
  | integer()