fact: Definition find_pivot m n (A : 'M[E]_(m.+1, n.+1)) : option ('I_m.+1 * 'I_n.+1) := pick [pred ij | A ij.1 ij.2 != 0].
imports: mathcomp(all_ssreflect) mathcomp(all_algebra) mathcomp(all_fingroup) mathcomp(all_real_closed) CoqEAL(binetcauchy ssrcomplements mxstructure minor) CoqEAL(smith dvdring polydvd) CoqEAL(similar perm_eq_image)