proposition: Lemma prl_r3_res3 i: inc i prl_r3_nI -> prl_r3_gij (J i i) = identity (prl_r3_Fl i).
proof: Proof. move => iL; rewrite /prl_r3_gij pr1_pair pr2_pair prl_r3_res0. apply:prl_restr_trivial. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)