Questions about the EntropyCoder?

I want to know the parameters accepted by EntropyBottleneck and GaussianConditional and their processing. Can you explain it a little bit? 

And what is the EntropyCoder used in this project? I only saw import ans/range_coder, but did not see their specific content. I want to implement these functions on hardware, so this is very important to me.

Thank you very much.