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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def unregister_controllers(self):
 """Destroy controller objects and clear internal registry. This will be called after each test class. """

        # TODO(xpconanfan): actually record these errors instead of just
        # logging them.
        for name, module in self._controller_modules.items():
            logging.debug('Destroying %s.', name)
            with expects.expect_no_raises(
                    'Exception occurred destroying %s.' % name):
                module.destroy(self._controller_objects[name])
        self._controller_objects = collections.OrderedDict()
        self._controller_modules = {}