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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 delete_all(self):
        '''
        Delete all keys
        '''
        for status, keys in six.iteritems(self.list_keys()):
            for key in keys:
                try:
                    os.remove(os.path.join(self.opts['pki_dir'], status, key))
                    eload = {'result': True,
                             'act': 'delete',
                             'id': key}
                    self.event.fire_event(eload,
                                          salt.utils.event.tagify(prefix='key'))
                except (OSError, IOError):
                    pass
        self.check_minion_cache()
        if self.opts.get('rotate_aes_key'):
            salt.crypt.dropfile(self.opts['cachedir'], self.opts['user'])
        return self.list_keys()