docs: def get_data_by_slug(model, slug, kind='', **kwargs):
      """Get instance data by slug and kind. Raise 404 Not Found if there is no data.
  
      This function requires model has a `slug` column.
  
      :param model: a string, model name in rio.models
      :param slug: a string used to query by `slug`. This requires there is a
                   slug field in model definition.
      :param kind: a string specified which kind of dict tranformer should be called.
      :return: a dict or None.
      """
  
      instance = get_instance_by_slug(model, slug, **kwargs)
  
      if not instance:
          return
  
      return ins2dict(instance, kind)