def METHOD_NAME(self, model_instances):
    # Include records needed by the initial value of the field plus any added 
    # via the extra_prefetch property.
    prefetch_set = set(model_instances) if model_instances else set()
    prefetch_set = prefetch_set.union(set(self.extra_prefetch))  # eliminate duplicates
    return sorted(
        select2_id_name(list(prefetch_set)),
        key=lambda item: unidecode.unidecode(item['text']),
    )