The polytope associated to a toric quiver is defined in terms of the stable spanning trees for that given quiver, and hence its vertices are in a lower dimensional subspace of the space with dimension $|Q_1|$. Thus a lower dimensional basis is useful for viewing polytopes in the appropriate dimension.
i1 : basisForFlowPolytope bipartiteQuiver(2,3)
o1 = | -1 0 |
| 0 -1 |
| 1 1 |
| 1 0 |
| 0 1 |
| -1 -1 |
6 2
o1 : Matrix ZZ <--- ZZ
|
i2 : basisForFlowPolytope ({0,1,4,5}, bipartiteQuiver(2,3))
o2 = | 0 1 |
| 1 -1 |
| -1 0 |
| 0 -1 |
| -1 1 |
| 1 0 |
6 2
o2 : Matrix ZZ <--- ZZ
|
The object basisForFlowPolytope is a method function.