fact: Definition isInterval {X:hSet} (S:hsubtype X) (T:WOSubset X) (le : S ⊆ T) : LEM -> sub_initial le -> T ⊈ S -> ∃ t:T, S ≡ upto t.
imports: UniMath.MoreFoundations.DecidablePropositions UniMath.MoreFoundations.Propositions UniMath.MoreFoundations.Subtypes UniMath.MoreFoundations.Sets UniMath.MoreFoundations.AxiomOfChoice UniMath.Combinatorics.OrderedSets