Remove cached results from this table's computed columns.

def clear_cached(self):
        """
        Remove cached results from this table's computed columns.

        """
        _TABLE_CACHE.pop(self.name, None)
        for col in _columns_for_table(self.name).values():
            col.clear_cached()
        logger.debug('cleared cached columns for table {!r}'.format(self.name))