presto-client/src/main/java/io/prestosql/client/OkHttpUtil.java/OkHttpUtil/setupProxy
class OkHttpUtil:    public static void setupProxy(OkHttpClient.Builder clientBuilder, Optional<HostAndPort> proxy, Proxy.Type type)
    {
        proxy.map(OkHttpUtil::toUnresolvedAddress)
                .map(address -> new Proxy(type, address))
                .ifPresent(clientBuilder::proxy);
    }