Returns list of matching VRFs

def complete_vrf(arg):
    """ Returns list of matching VRFs
    """

    search_string = ''
    if arg is not None:
        search_string = '^%s' % arg

    res = VRF.search({
        'operator': 'regex_match',
        'val1': 'rt',
        'val2':  search_string
        }, { 'max_result': 100000 } )

    ret = []

    for v in res['result']:
        ret.append(v.rt)
    if re.match(search_string, 'none'):
        ret.append('none')

    return ret