fact: Definition tanner_rel' : rel ('I_ m + 'I_n) := fun x y => match x, y with | inl x', inr y' => H x' y' == 1 | inr x', inl y' => H y' x' == 1 | _, _ => false end.
imports: mathcomp(all_ssreflect ssralg fingroup finalg perm zmodp) mathcomp(matrix) bigop_ext ssralg_ext f2 subgraph_partition