Type@{A} := {X : 𝒫 (𝒫 (𝒫 A)) | smalltype (merely (exists a, uni_fix (hartogs_number'_injection.
From HoTT Require Import TruncType ExcludedMiddle Modalities.ReflectiveSubuniverse abstract_algebra HSet. From HoTT Require Import Universes.Smallness. From HoTT Require Import Spaces.Card. From HoTT.Sets Require Import Ordinals Powers.