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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 is_blacklisted(self, appid, crawlid):
        '''
        Checks the redis blacklist for crawls that should not be propagated
        either from expiring or stopped
        @return: True if the appid crawlid combo is blacklisted
        '''
        key_check = '{appid}||{crawlid}'.format(appid=appid,
                                                crawlid=crawlid)
        redis_key = self.spider.name + ":blacklist"
        return self.redis_conn.sismember(redis_key, key_check)