def unit_name(service, parent=None, group=None, version='latest'):
    """Return the houston standard service name that can be reverse parsed by
    the parse

    :param str service: The service name
    :param str|None parent: An optional parent for the service
    :param str|None group: An optional deployment group
    :param str|None version: An optional service version
    :rtype: str

    """
    parts = []
    if parent is not None and parent != service:
        parts += [parent, '.']
    parts += [service]
    if group is not None:
        parts += [':', group]
    parts += ['@', version or 'latest', '.service']
    return ''.join(parts)