'Return the item id for item_name (case-insensitive)'

@read_api
def get_item_ids(self, field, item_names):

    rmap = {(icu_lower(v) if isinstance(v, unicode) else v): k for (k, v) in self.fields[field].table.id_map.iteritems()}
    return {name: rmap.get((icu_lower(name) if isinstance(name, unicode) else name), None) for name in item_names}
