Make.Xval load_file : 
  t ->
  path:Fpath_sexp0.Absolute_path.t ->
  (string, Pplumbing_err.Err.t) Stdlib.Result.tval save_file : 
  t ->
  ?perms:int ->
  unit ->
  path:Fpath_sexp0.Absolute_path.t ->
  file_contents:string ->
  (unit, Pplumbing_err.Err.t) Stdlib.Result.tval read_dir : 
  t ->
  dir:Fpath_sexp0.Absolute_path.t ->
  (Fpath_sexp0.Fsegment.t list, Pplumbing_err.Err.t) Stdlib.Result.t