def always_tuple(value, none=()):
    """
    Some arguments can be a single value, or a sequence (tuple or list).
    This function normalizes the input to always be a sequence.

    :param value: The value that, if non-sequence, should be converted to a
                  sequence
    :param none: Value returned when input is None
    :return: The value as a sequence.
    """
    if value is None:
        return none
    elif hasattr(value, '__iter__') and not isinstance(value, str):
        return tuple(value)
    else:
        return value,
