def ni(i):
    """
    Return a usable interval. Note that ni accepts D W and M but we are not  going
    to use them in structjour.
    :return: The given argument if its supported or 1, enabling resample for all other (int) values
    """
    supported = [1, 2, 5, 15, 60]
    if i in supported:
        return i
    elif isinstance(i, int):
        return 1
    return 5
