Batteries user guide : BatLazyList.Labels.Exceptionless

`sig
val find : f:('a -> bool) -> 'a BatLazyList.t -> 'a option
val rfind : f:('a -> bool) -> 'a BatLazyList.t -> 'a option
val findi : f:(int -> 'a -> bool) -> 'a BatLazyList.t -> (int * 'a) option
val rfindi : f:(int -> 'a -> bool) -> 'a BatLazyList.t -> (int * 'a) option
val split_at :
int ->
'a BatLazyList.t ->
[ `Invalid_index of int | `Ok of 'a BatLazyList.t * 'a BatLazyList.t ]
val at : 'a BatLazyList.t -> int -> [ `Invalid_index of int | `Ok of 'a ]
val assoc : 'a -> ('a * 'b) BatLazyList.t -> 'b option
val assq : 'a -> ('a * 'b) BatLazyList.t -> 'b option
end`