Section CardFunImage.
Variables aT aT2 rT : finType.
Variables (f : aT -> rT) (g : rT -> aT) (f2 : aT -> aT2 -> rT).
Variables (D : pred aT) (D2 : pred aT).

Lemma imset_id (T : finType) (A : {set T}) : [set x | x in A] = A.