docs: def serialize_m2m_on_save(sender, action, instance, using, **kwargs):
      """ Part of the serialize transaction process that ensures m2m are
      serialized correctly.
  
      Skip those not registered.
      """
      if action == "post_add":
          try:
              wrapped_instance = site_offline_models.get_wrapped_instance(instance)
          except ModelNotRegistered:
              pass
          else:
              wrapped_instance.to_outgoing_transaction(using, created=True)