Return list of ports found by the provider

def portname_list(providername=None):
    """
    Return list of ports found by the provider
    """
    _providername = providername
    if not _providername:
        _providername = provider_check()

    import_str = 'netshowlib.%s.iface' % _providername
    return import_module(import_str).portname_list()