// Cells and their vertices.
#0={0}
#1={1,3,9}
#2={2,5,8}
#3={4,6,7}

// Induced graph on cells.
#0:.
#1:->#0.
#2:->#0.
#3:->#1,#2.

// Individual cells.
// cell #0:
0[0]: {}

// cell #1:
0[1]: {3} --> 1
1[3]: {2} --> 0,2
2[9]: {1} --> 1

// cell #2:
0[2]: {1} --> 1
1[5]: {2} --> 0,2
2[8]: {3} --> 1

// cell #3:
0[4]: {1,3} --> 1,2
1[6]: {2,3} --> 0
2[7]: {1,2} --> 0