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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 reset_permission_factories(self):
 """Remove cached permission factories."""

        for key in ('read', 'create', 'update', 'delete'):
            full_key = '{0}_permission_factory'.format(key)
            if full_key in self.__dict__:
                del self.__dict__[full_key]