There seems to be a bug in Cadabra 1.42 in the unwrap routine for anticommuting objects.

The below is a minimal example that produces it.

```
{A, B, C}::AntiCommuting.
d{#}::Derivative.
A::Depends(d).
B::Depends(d).
```

The following produces "-C d{A B}" erroneously. The sign seems to be produced as long as there is at least one anticommuting object inside.

```
d{A B C}: @unwrap!(%);
```

If we apply product rule first, this produces "dA B C + A dB C" correctly.

```
d{A B C}: @prodrule!(%): @unwrap!(%)
```