Core_via_kleisli_composition.Reqinclude Preface_specs.Indexed_monad.WITH_RETURN_AND_KLEISLI_COMPOSITION
with type ('a, 'index) t := 'a tinclude Preface_specs.Indexed_monad.WITH_RETURN
with type ('a, 'index) t := 'a tval return : 'a -> 'a tLift a value into a t.