def bubble_down(lst: list, start: int, end: int) -> None:
    """Bubble down through <lst> from indexes <end> through <start>, swapping
    items that are out of place.

    >>> L = [4, 3, 2, 1, 0]
    >>> bubble_down(L, 1, 3)
    >>> L
    [4, 1, 3, 2, 0]
    """
    i = end
    while i > start:

        if lst[i] < lst[i - 1]:
            lst[i], lst[i - 1] = lst[i - 1], lst[i]

        i -= 1

    return None