<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def resolve_filenames(all_expr):
 """resolve expression for a filename :param all_expr: A comma separated list of expressions. The expressions can contain the wildcard characters ``*`` and ``?``. It also resolves Spark datasets to the paths of the individual partitions (i.e. ``my_data`` gets resolved to ``[my_data/part-00000, my_data/part-00001]``). :returns: A list of file names. :rtype: list """

        files = []
        for expr in all_expr.split(','):
            expr = expr.strip()
            files += fs.get_fs(expr).resolve_filenames(expr)
        log.debug('Filenames: {0}'.format(files))
        return files