'fetch proxy into Db by ProxyGetter
:return:'

def refresh(self):

    for proxyGetter in self.config.proxy_getter_functions:
        proxy_set = set()
        for proxy in getattr(GetFreeProxy, proxyGetter.strip())():
            if proxy.strip():
                self.log.info('{func}:    fetch    proxy    {proxy}'.format(func=proxyGetter, proxy=proxy))
                proxy_set.add(proxy.strip())
        self.db.changeTable(self.raw_proxy_queue)
        for proxy in proxy_set:
            self.db.put(proxy)
