Description: A deduction unionizing a non-unionized collection of virtual hypotheses.
3anidm12 denotes the deduction which would have been named uun112 if
it did not pre-exist in set.mm. This second permutation's name is based
on this pre-existing name. (Contributed by Alan Sare, 4-Feb-2017)(Proof modification is discouraged.)(New usage is discouraged.)