<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def do_cleaning(self, arg):
 """Does the actual cleaning by using the delete methods above. :param arg: A string, the string which shell be cleaned. Or a list, in which case each of the strings within the list is cleaned. :return: A string, the cleaned string. Or a list with cleaned string entries. """

        if arg is not None:
            if isinstance(arg, list):
                newlist = []
                for entry in arg:
                    newlist.append(self.do_cleaning(entry))
                return newlist
            else:
                if sys.version_info[0] < 3:
                    arg = unicode(arg)
                else:
                    arg = str(arg)
                arg = self.delete_tags(arg)
                arg = self.delete_whitespaces(arg)
                return arg
        else:
            return None