'Sort column using case-insensitive alphabetical sorting on item\'s username.'

def sort(self, trans, query, ascending, column_name=None):

    if ascending:
        query = query.order_by(func.lower(self.model_class.username).asc())
    else:
        query = query.order_by(func.lower(self.model_class.username).desc())
    return query
