<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def list_services():
 """ returns list of available services """

    for importer, modname, ispkg in pkgutil.iter_modules(services.__path__):
        if ispkg is False:
            importer.find_module(modname).load_module(modname)

    services_list = list()
    for s in services.serviceBase.__subclasses__():
        services_list.append(s.__name__.lower())

    return services_list