fact: Definition reindex_carrier_union {X : UU} {I J : UU} (index : I → hsubtype X) (g : J → I) : (carrier (⋃ (index ∘ g))) → (carrier (⋃ index)).
imports: UniMath.Foundations.Propositions UniMath.MoreFoundations.PartA UniMath.MoreFoundations.Notations UniMath.Combinatorics.FiniteSets UniMath.Combinatorics.StandardFiniteSets UniMath.MoreFoundations.Subtypes UniMath.Combinatorics.KFiniteTypes