Continuation lines indented by four more spaces makes it consistent. I personally don't think it looks bad. Writing
```
    assert H == h \
        and R.dmp_mul(H, cff) == f \
        and R.dmp_mul(H, cfg) == g 
```
would make the code aligned as you apparently wish it was and the automatic indentation script wouldn't change it. In any case I would think that this particular change is a very small loss to the overall gain.