Instant JAZZ

Instant JAZZ
Create a function which concatenates the number 7 to the end of every chord in a list. Ignore all chords which already end with 7.

Examples
jazzify(["G", "F", "C"]) ➞ ["G7", "F7", "C7"]

jazzify(["Dm", "G", "E", "A"]) ➞ ["Dm7", "G7", "E7", "A7"]

jazzify(["F7", "E7", "A7", "Ab7", "Gm7", "C7"]) ➞ ["F7", "E7", "A7", "Ab7", "Gm7", "C7"]

jazzify([]) ➞ []

["G", "F", "C"]
["Dm", "G", "E", "A"]