<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def listify(args):
 """Return args as a list. If already a list - return as is. [1, 2, 3] If a set - return as a list. [1, 2, 3] If a tuple - return as a list. [1, 2, 3] If a generator (also range / xrange) - return as a list. [1, 2, 3] [1, 2, 3] [1, 2, 3] If a single instance of something that isn't any of the above - put as a single element of the returned list. [1] If "empty" (None or False or '' or anything else that evaluates to False), return an empty list ([]). [] [] [] [] [] """

    if args:
        if isinstance(args, list):
            return args
        elif isinstance(args, (set, tuple, GeneratorType,
                               range, past.builtins.xrange)):
            return list(args)
        return [args]
    return []