proc is_valid(templ: Template): bool {....raises: [Exception], tags: [RootEffect],
                                       forbids: [].}

proc Template(s: string): Template {....raises: [], tags: [], forbids: [].}

iterator get_identifiersMayDup(templ: Template): string {....raises: [Exception],
    tags: [RootEffect], forbids: [].}

template genSubstitute(M; Key; sym; doExc) {.dirty.}