fact: Definition embed x := if x \in ac then h x else if edge x \in ac then edge (h (edge x)) else if node x \in ac then face (edge (h (node x))) else edge (node (node (h (node (edge x))))).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color chromogram coloring patch) fourcolor(snip revsnip kempe birkhoff contract)