It was e for edge, now k for keys. Why? I'm toying with ideas
for a full Tutte Coxeter graph (30 vertices/nodes/GPIO pins,
45 edges/switches) incuding 42 keys plus a rotary encoder
(these act like three switches: clockwise, anticlockwise,
press - so 42 edges for normal keys + 3 edges for a rotary
encoder gives 42 + 3 = 45 edges) which could be named with
suffix 43ke.
