(lists/keep (fn [x] (if (comparison/identical? .x 0) null .x)) [0 1 false 2])
(lists/keep :fn/identity [null false 1])
(lists/keep :fn/identity [])
(lists/keep :fn/identity null)
(lists/keep :fn/identity [null null])
(lists/keep :fn/identity [false 0 "" [] {}])
(lists/keep (fn [x] (* .x 2)) [1 2 3])
(lists/keep (fn [x] [.x]) [a b])