Filtration: a, b, c, d, cd, bd, ac
R(cd) = c + d
R(bd) = b + c
R(ac) = a + b
P = [('d', 'cd'), ('c', 'bd'), ('b', 'ac')]
Independent union-find pairing: AGREES
V_P = [('d', 'cd')]
Modified Hasse diagram: ACYCLIC
Paths bd -> c: 1
  bd -> d -> cd -> c
Paths ac -> b: 0
VERIFIED: (b,ac) is a nonincident persistence pair with ZERO gradient paths.
