(check-expect (count '(1 2 3)) 3)
(check-expect (count '(1 (2 (3)))) 3)
(check-expect (count '(("hello") "hello" ("hello") "hello" "hello")) 5)
(check-expect (count '(() (() (()) (((0)))))) 1)
(check-expect (count '((0) (1 (2) (3) ((4) ())))) 5)
(check-expect (count '(0 1 (2) ((3) ((4) (5 6 7 (8) (9) ()))))) 10)
(check-expect (count-matching odd? '(1 2 3)) 2)
(check-expect (count-matching odd? '(1 (2 (3)))) 2)
(check-expect (count-matching even? '((0) (1 (2) (3) ((4) ())))) 3)
(check-expect
 (count-matching number? '(0 (2) ((3) ((4) (5 (8) ("nine") ()))))) 6)