code: def level(self, website=None, store_view=None, parent_category=None):
          
          return self.call(
              'catalog_category.level', [website, store_view, parent_category]
          )
docs: Retrieve one level of categories by website/store view/parent category
  
          :param website: Website code or ID
          :param store_view: storeview code or ID
          :param parent_category: Parent Category ID
          :return: Dictionary