def get_keys(data_list, leading_columns=LEADING_COLUMNS):
    all_keys = set().union(*(list(d.keys()) for d in data_list))
    leading_keys = []
    for key in leading_columns:
        if key not in all_keys:
            continue
        leading_keys.append(key)
        all_keys.remove(key)
    return leading_keys + sorted(all_keys)