Module type Map_reduce.Map_reduce_function_with_init_spec
module Param : Core.Binablemodule Accum : Core.Binablemodule Input : Core.Binableval init : Param.t -> state_type Async.Deferred.tval map : state_type -> Input.t -> Accum.t Async.Deferred.tval combine : state_type -> Accum.t -> Accum.t -> Accum.t Async.Deferred.t