Definition seq_countMixin := CountMixin pickle_seqK.Canonical seq_countType := Eval hnf in CountType (seq T) seq_countMixin.Structure subCountType : Type :=
  SubCountType {subCount_sort :> subType P; _ : mixin_of subCount_sort}.Structure subCountType : Type :=
  SubCountType {subCount_sort :> subType P; _ : mixin_of subCount_sort}.Structure subCountType : Type :=
  SubCountType {subCount_sort :> subType P; _ : mixin_of subCount_sort}.

Lemma pickle_taggedK : pcancel pickle_tagged unpickle_tagged.