def order(sentence: str) -> str:
    """Returns ordered sentence.

    Examples:
        >>> assert order("") == ""
        >>> assert order("is2 Thi1s T4est 3a") == "Thi1s is2 3a T4est"
    """
    return " ".join(
        map(
            lambda item: item[1],
            sorted(
                map(
                    lambda word: (
                        [index for index in word if index.isdigit()][0],
                        word,
                    ),
                    sentence.split(),
                )
            ),
        )
    )