`sig
type t = (string, string) Core.Std.List.Assoc.t
val add : key:string -> data:string -> Environment.t -> Environment.t
val find : key:string -> Environment.t -> string option
val find_exn : key:string -> Environment.t -> string
val mem : key:string -> Environment.t -> bool
val remove : key:string -> Environment.t -> Environment.t
val import_from_sys :
?default:string -> key:string -> Environment.t -> Environment.t
val append_to_path :
?where:[ `Back | `Front ] ->
key:string -> data:string -> Environment.t -> Environment.t
val to_exec_env : Environment.t -> string list
val of_exec_env : string array -> Environment.t
end`