fact: Definition is_subalgebra_class (s : Sort σ) (x : (A/Φ) s) : HProp := hexists (λ (y : (A&&P) s), in_class (Φ s) x (i s y)).
imports: HSet Colimits.Quotient Classes.interfaces.canonical_names Classes.theory.ua_isomorphic Classes.theory.ua_subalgebra Classes.theory.ua_quotient_algebra