It's not currently implemented for:
- elements of Rees matrix semigroups;
- elements of regular Rees 0-matrix semigroups over non-groups;
- elements of free bands;
- PBRs;
- Matrices over semirings (other than finite fields);
- there are probably more.
Also harmonise OnePseudoInverseOfSemigroupElement and OneInverseOfSemigroupElement by having a 1 argument version and a 2 argument version for them both (currently OnePseudoInverseOfSemigroupElement takes 1 argument, and OneInverseOfSemigroupElement always takes 2 arguments).