<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def register_classes(self, classes):
 """ Register classes as plugins that are not subclassed from IPlugin. `classes` may be a single object or an iterable. """

        classes = util.return_list(classes)
        for klass in classes:
            IPlugin.register(klass)