Write a function cond_dup : 'a list -> ('a -> bool) -> 'a list that takes in a list and preciate and duplicates all elements which satisfy the condition expressed in the predicate. For example, cond_dup [3;4;5] (fun x -> x mod 2 = 1) = [3;3;4;5;5]. let rec cond_dup l f = (* YOUR CODE HERE *) raise (Failure "Not implemented") assert (cond_dup [3;4;5] (fun x -> x mod 2 = 1) = [3;3;4;5;5])