IsSelfDualSemigroup returns false negatives

[james-d-mitchell]

For example, with only Smallsemi loaded:

gap> S := SmallSemigroup(6, 2);;
gap> IsSelfDualSemigroup(S);
true

with Semigroups loaded:

gap> S := SmallSemigroup(6, 2);;
gap> IsSelfDualSemigroup(S);
false

The correct answer seems to be the one returned by Smallsemi, since:

gap> S := SmallSemigroup(6, 2);;
gap> T := DualSemigroup(S);;
gap> IsIsomorphicSemigroup(S, T);
true

The issue is that the generators don't have to be mapped by the identity function from T to Range(map) in:

Semigroups/gap/attributes/properties.gi

Lines 1651 to 1657 in fa9344f

	T := AsSemigroup(IsFpSemigroup, S);
	map := AntiIsomorphismDualFpSemigroup(T);
	return SemigroupIsomorphismByImages(T,
	Range(map),
	GeneratorsOfSemigroup(T),
	List(GeneratorsOfSemigroup(T),
	x -> x ^ map)) <> fail;

gap> S := SmallSemigroup(6, 2);;
gap> OnTuples(GeneratorsOfSemigroup(S), map); 
[ m1, m2, m3, m4, m6, m5 ]