(U1) the image L and its rank <= 2 locus
  [ok] (U1) a2 = 0: the shift lies in L identically in (c1, c3) (symbolic)
  [ok] (U1) a2 = 0: dim L = 17; shift in L on 5 sample A: True; rank 7 of h -> sum l_i h_i for every lambda != 0 (radical of the 7x7 minors = (l1,l2,l3)): True
  [ok] (U1) a2 = 1: the shift lies in L identically in (c1, c3) (symbolic)
  [ok] (U1) a2 = 1: dim L = 18; shift in L on 5 sample A: True; rank 7 of h -> sum l_i h_i for every lambda != 0 (radical of the 7x7 minors = (l1,l2,l3)): True
(A2) members and certificates
  [ok] (A2) a2 = 0: member closed with H and D_3 = N_3 at a random point of the rank-2 locus; S6.2 triple of local length 35 <= 41
  [ok] (A2) a2 = 1: member closed with H and D_3 = N_3 at a random point of the rank-2 locus; S6.2 triple of local length 35 <= 41
6 checks, 0 failed
ALL CHECKS PASSED
