fact: Definition grid_map := let: GmCutout G _ _ _ _ _ _ _ _ _ := has_cutout in dual G.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph order ssralg ssrnum ssrint) fourcolor(hypermap geometry color coloring patch snip grid) fourcolor(matte)