def bubble_up(lst: list, start: int, end: int) -> None:
    """Bubble up through L[start:end], swapping items that are out of order.

    >>> L = [4, 3, 2, 1, 0]
    >>> bubble_up(L, 0, 3)
    >>> L
    [3, 2, 1, 4, 0]
    >>> L = [4, 3, 2, 1, 0]
    >>> bubble_up(L, 2, 4)
    >>> L
    [4, 3, 1, 0, 2]
    """
    for i in range(start, end):

        if lst[i] > lst[i + 1]:
            lst[i], lst[i + 1] = lst[i + 1], lst[i]

    return None