The moment graph of a GKM variety $X$ with an action of a torus $T$ has vertices corresponding to the $T$-fixed points $X^T$ and edges corresponding to the one-dimensional $T$-orbits. If $\{v_1,v_2\}$ is an edge and the corresponding one-dimensional $T$-orbit closure is $\mathbb P^1$ where $v_1 = 0$ and $v_2 = \infty$, then denote $m(v_1,v_2)$ to be the negative of the character of the action of $T$ on $\mathbb A^1 \subset \mathbb P^1$ (where $v_1 \in \mathbb A^1$).
A MomentGraph is a HashTable with three keys:
Functionalities concerning intersection cohomology of sheaves on moment graphs, which had been implemenented before (see MG: moment graph computations), have not been imported into this package yet.
The object MomentGraph is a type, with ancestor classes HashTable < Thing.