module Output:sig..end
wait t closes stdin t and then begins collecting the output produced on t's
    stdout and stderr, continuing to collect output until t terminates.  As usual,
    other async jobs can run before the deferred returned by wait becomes determined.type t = {
   | 
stdout : | 
   | 
stderr : | 
   | 
exit_status : | 
val sexp_of_t : t -> Sexplib.Sexp.t