Irish lowercase with ICU

import icu

def transliterator_from_rules(name, rules):
    fromrules = icu.Transliterator.createFromRules(name, rules)
    icu.Transliterator.registerInstance(fromrules)
    return icu.Transliterator.createInstance(name)

irishlc_rules = """
:: NFD;
$uvowel=[AEIOU];
$wb=[^[:L:][:M:]];
$wb { ([nt]) } $uvowel → $1 '-';
:: lower;
:: NFC;
"""

irishlc = transliterator_from_rules('irishlc', irishlc_rules)

irishlc.transliterate("tá an tUachtarán tar éis a lámh a chur leis")

'tá an t-uachtarán tar éis a lámh a chur leis'