code: def list(self, link_type, product, identifierType=None):
          
          return self.call('catalog_product_link.list',
                           [link_type, product, identifierType])
docs: Retrieve list of linked products
  
          :param link_type: type of link, one of 'cross_sell', 'up_sell',
                  'related' or 'grouped'
          :param product: ID or SKU of product
          :param identifierType: Defines whether the product or SKU value is
                                 passed in the "product" parameter.
  
          :return: `list` of `dict`