fact: Definition M := \matrix_(i,j < 2) 1%:Z.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq ssralg) mathcomp(path choice fintype tuple finset bigop poly matrix mxpoly) CoqEAL(hrel param refinements trivial_seq) mathcomp(ssrint poly) CoqEAL(binnat binint seqpoly binord)