def parse_list_option(opt):
    """Parse options as list.

    Strings are split based on comma separated elements.
    Result is sorted.

    >>> parse_list_option('')
    []
    >>> parse_list_option('opt1,opt2,opt3')
    ['opt1', 'opt2', 'opt3']
    >>> parse_list_option(['opt1','opt3','opt2'])
    ['opt1', 'opt2', 'opt3']
    """
    if not opt:
        return []
    if isinstance(opt, (list, tuple)):
        return sorted(opt)
    return sorted(opt.split(","))