(lefts loc)
Returns a seq of the left siblings of this loc
(def vz (vector-zip [1 2 3 4 5]))
;; root
;; |________
;; | | | | |
;; 1 2[3]4 5
;;go down and then right twice, what's to the left of me now?
(-> vz down right right lefts)
=>(1 2)
;;equivalent:
(-> vz down right right rights)
=>(4 5)