def get_block_params(self):
        """ Auxiliary method to obtain ``ref_block_num`` and
            ``ref_block_prefix``. Requires a websocket connection to a
            witness node!
        """
        ws = self.blockchain.rpc
        dynBCParams = ws.get_dynamic_global_properties()
        ref_block_num = dynBCParams["head_block_number"] & 0xFFFF
        ref_block_prefix = struct.unpack_from(
            "<I", unhexlify(dynBCParams["head_block_id"]), 4
        )[0]
        return ref_block_num, ref_block_prefix