docs: def cleanup_handlers(event=None):
      """Remove handlers of a given `event`. If no event is informed, wipe
      out all events registered.
  
      Be careful!! This function is intended to help when writing tests
      and for debugging purposes. If you call it, all handlers associated
      to an event (or to all of them) will be disassociated. Which means
      that you'll have to reload all modules that teclare handlers. I'm
      sure you don't want it.
      """
      if event:
          if event in HANDLER_REGISTRY:
              del HANDLER_REGISTRY[event]
          if event in EXTERNAL_HANDLER_REGISTRY:
              del EXTERNAL_HANDLER_REGISTRY[event]
      else:
          HANDLER_REGISTRY.clear()
          EXTERNAL_HANDLER_REGISTRY.clear()