code: def save(self):
          
          if self.code:
              raise HolviError("Orders cannot be updated")
          send_json = self.to_holvi_dict()
          send_json.update({
              'pool': self.api.connection.pool
          })
          url = six.u(self.api.base_url + "order/")
          stat = self.api.connection.make_post(url, send_json)
          code = stat["details_uri"].split("/")[-2]  # Maybe slightly ugly but I don't want to basically reimplement all but uri formation of the api method
          return (stat["checkout_uri"], self.api.get_order(code))
docs: Saves this order to Holvi, returns a tuple with the order itself and checkout_uri