Return a set of attributes for a multiple items in
        multiple tables using their primary keys.

        :type request_items: dict
        :param request_items: A Python version of the RequestItems
            data structure defined by DynamoDB.

def batch_get_item(self, request_items, object_hook=None):
        """
        Return a set of attributes for a multiple items in
        multiple tables using their primary keys.

        :type request_items: dict
        :param request_items: A Python version of the RequestItems
            data structure defined by DynamoDB.
        """
        data = {'RequestItems' : request_items}
        json_input = json.dumps(data)
        return self.make_request('BatchGetItem', json_input,
                                 object_hook=object_hook)