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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 _get_generator_plugins(cls):
 """ Return a list of classes from external plugins that are used to generate checker classes """


        if not hasattr(cls, 'suite_generators'):
            gens = working_set.iter_entry_points('compliance_checker.generators')
            cls.suite_generators = [x.resolve() for x in gens]

        return cls.suite_generators