Subset​(AngouriMath.​Entity,​AngouriMath.​Entity,​System.​Boolean)

Whether every member of sub is a member of super,
as a truth value, or null where that is not settled. Both sets arrive
already simplified. The routes, in order: what the two shapes say outright, what the
set algebra says about a union, an intersection, a difference or a power set on either
side, the members of a finite set one by one, the chain the special sets sit on, the
ends of two intervals, the difference sub \ super where it evaluates, and last
the statement forall x in sub : x in super, which the quantifier decision
answers with the solver where the membership reads as a comparison.
https://github.com/asc-community/AngouriMath/issues/1409