I feel very strongly that you shouldn't do this. I believe it's a consequence of doing the negotiation and storing of axis in the CoordSignatures rather than the containing ProtoCube. Most significantly it means that doing ```a == b``` can modify both ```a``` and ```b``` (sometimes just ```b```). Interestingly it also means the ```a == b``` is quite different to ```b == a```. In my opinion this kind of thing should not be going on in ```__eq__```.