cannot uninstall - D7 code un D6 version

Trying to uninstall:
Fatal error: Call to undefined function db_delete() in .../sites/all/modules/switchtheme/switchtheme.install on line 12

in switchtheme.inc:

function switchtheme_uninstall() {
- db_delete('variable')
- ->condition('name', 'switchtheme_%', 'LIKE')
- ->execute();
+ db_query("DELETE FROM {variable} WHERE name LIKE 'switchtheme_%'");
}