code: def call(self, items, additional_fields, shape):
          
          return self._pool_requests(payload_func=self.get_payload, **dict(
              items=items,
              additional_fields=additional_fields,
              shape=shape,
          ))
docs: Returns all items in an account that correspond to a list of ID's, in stable order.
  
          :param items: a list of (id, changekey) tuples or Item objects
          :param additional_fields: the extra fields that should be returned with the item, as FieldPath objects
          :param shape: The shape of returned objects
          :return: XML elements for the items, in stable order