def is_sequence(arg):
    """
    Checks to see if something is a sequence (list).

    Parameters
    ----------
    arg : str
        The string to be examined.

    Returns
    -------
    sequence : bool
        Is True if `arg` is a list.

    """
    sequence = not hasattr(arg, 'strip') and hasattr(arg, '__getitem__'
        ) or hasattr(arg, '__iter__')
    return sequence
