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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 check_minion_cache(self, preserve_minions=None):
        '''
        Check the minion cache to make sure that old minion data is cleared

        Optionally, pass in a list of minions which should have their caches
        preserved. To preserve all caches, set __opts__['preserve_minion_cache']
        '''
        if preserve_minions is None:
            preserve_minions = []
        keys = self.list_keys()
        minions = []
        for key, val in six.iteritems(keys):
            minions.extend(val)
        if not self.opts.get('preserve_minion_cache', False):
            m_cache = os.path.join(self.opts['cachedir'], self.ACC)
            if os.path.isdir(m_cache):
                for minion in os.listdir(m_cache):
                    if minion not in minions and minion not in preserve_minions:
                        try:
                            shutil.rmtree(os.path.join(m_cache, minion))
                        except (OSError, IOError) as ex:
                            log.warning('Key: Delete cache for %s got OSError/IOError: %s \n',
                                        minion,
                                        ex)
                            continue
            cache = salt.cache.factory(self.opts)
            clist = cache.list(self.ACC)
            if clist:
                for minion in clist:
                    if minion not in minions and minion not in preserve_minions:
                        cache.flush('{0}/{1}'.format(self.ACC, minion))