Mark a proxy as good

def mark_good(self, proxy):
        """ Mark a proxy as good """
        if proxy not in self.proxies:
            logger.warn("Proxy <%s> was not found in proxies list" % proxy)
            return

        if proxy not in self.good:
            logger.debug("Proxy <%s> is GOOD" % proxy)

        self.unchecked.discard(proxy)
        self.dead.discard(proxy)
        self.good.add(proxy)
        self.proxies[proxy].failed_attempts = 0