ensure `pack` structures are the same as their wrapped ones

It seems like these are not the same after wrapping

```python
import rdkit2ase

benzene = rdkit2ase.smiles2conformers("c1ccccc1", numConfs=1)

# Pack a box with 10 benzene molecules
box = rdkit2ase.pack(
    data=[benzene],
    counts=[10],
    density=800,
    packmol="packmol.jl",
)
```