No, not `return`. It still needs to compute the test. 

Also, since `coupled_DE_system` takes elements of the field, it should really be

```py
with DecrementLevel(DE):
    s1, s2 = coupled_DE_system(b1a, b1d, b2a, b2s, c1a, c1d, c2a, c2d, DE)
```

where `b1a` and so on are in the decremented `DE.t`.