Monad_sequence.S is a generic interface specifying functions that deal with a
container and a monad. It is specialized to the Deferred monad and used with
various containers in modules Deferred.Array, Deferred.List, Deferred.Queue, and
Deferred.Sequence. The Monad_sequence.how type specifies the parallelism of
container iterators.
val sexp_of_how : how ‑> Base.Sexp.tmodule type S : sig ... end