This method outputs the underlying undirected Graph of a moment graph.
i1 : G = momentGraph projectiveSpace 3
o1 = a "moment graph" on 4 vertices with 6 edges
o1 : MomentGraph
i2 : underlyingGraph G
o2 = Graph{set {0} => {set {1}, set {2}, set {3}}}
set {1} => {set {0}, set {2}, set {3}}
set {2} => {set {0}, set {1}, set {3}}
set {3} => {set {0}, set {1}, set {2}}
o2 : Graph