Complex map for walking tutorial

complex-map.clj

(def m {"1234" [{:alert 1,
                 :lines [{:column1 "val1", :column2 "val2", :column3 "val13"}
                         {:column1 "val3", :column2 "val4", :column3 "val14"}]}
                {:alert 2,
                 :lines [{:column1 "val5", :column2 "val6", :column3 "val15"}]}],
        "4455" [{:alert 4,
                 :lines [{:column1 "val7", :column2 "val8", :column3 "val16"}
                         {:column1 "val9", :column2 "val10", :column3 "val117"}]}
                {:alert 5,
                 :lines [{:column1 "val11", :column2 "val12", :column3 "val18"}]}]})

-- The goal structure
(def m1 {"1234" [{:alert 1,
                 :lines [{:column1 "val1", :column3 "val13"}
                         {:column1 "val3", :column3 "val14"}]}
                {:alert 2,
                 :lines [{:column1 "val5", :column3 "val15"}]}],
        "4455" [{:alert 4,
                 :lines [{:column1 "val7", :column3 "val16"}
                         {:column1 "val9", :column3 "val117"}]}
                {:alert 5,
                 :lines [{:column1 "val11",:column3 "val18"}]}]})

Without Specter:

(zipmap (keys m)
        (map (fn [v]
                 (mapv #(update % :lines
                                (fn [v]
                                    (mapv
                                     (fn [m]
                                         (dissoc m :column2)) v)))
                       v))
             (vals m)))

With Specter (with thanks to Nathan Marz):

(transform [ALL LAST ALL :lines ALL] #(dissoc % :column2) m)