code: def assignproduct(self, category_id, product, position=None):
          
          return bool(self.call(
              'catalog_category.assignProduct', [category_id, product, position])
          )
docs: Assign product to a category
  
          :param category_id: ID of a category
          :param product: ID or Code of the product
          :param position: Position of product in category
  
          :return: boolean