apply IsDeduct.assume_
case h1.h1.h1.a.h1
P Q : Formula
v : VarName
⊢ IsDeduct {forall_ v Q, forall_ v ((P.imp_ Q).and_ (Q.imp_ P))} (forall_ v Q)
case h1.h1.h1.a.h1.a
P Q : Formula
v : VarName
⊢ forall_ v Q ∈ {forall_ v Q, forall_ v ((P.imp_ Q).and_ (Q.imp_ P))}