code: def cancel_all(self, product_id=None):
          
          if product_id is not None:
              params = {'product_id': product_id}
          else:
              params = None
          return self._send_message('delete', '/orders', params=params)
docs: With best effort, cancel all open orders.
  
          Args:
              product_id (Optional[str]): Only cancel orders for this
                  product_id
  
          Returns:
              list: A list of ids of the canceled orders. Example::
                  [
                      "144c6f8e-713f-4682-8435-5280fbe8b2b4",
                      "debe4907-95dc-442f-af3b-cec12f42ebda",
                      "cf7aceee-7b08-4227-a76c-3858144323ab",
                      "dfc5ae27-cadb-4c0c-beef-8994936fde8a",
                      "34fecfbf-de33-4273-b2c6-baf8e8948be4"
                  ]