Where to get logstash kafka output plugin 4.x

Hi ,

I need to work on logstash kafka output plugin, and I need its version to be 4.xx ot 3.xxx.
I tried to checkout its branch on git hub, but it only have master branch(5.X) and a 2.x branch.

So where can I find the code branch for 4.xx or 3.xx?

Regards,
Da