vertices(HyperGraph) -- gets the vertices of a (hyper)graph

i1 : S = QQ[a..d];

i2 : g = graph {a*b,b*c,c*d,d*a} -- the four cycle

o2 = Graph{edges => {{a, b}, {b, c}, {a, d}, {c, d}}}
           ring => S
           vertices => {a, b, c, d}

o2 : Graph

i3 : vertices g

o3 = {a, b, c, d}

o3 : List

i4 : h = hyperGraph{a*b*c}

o4 = HyperGraph{edges => {{a, b, c}}    }
                ring => S
                vertices => {a, b, c, d}

o4 : HyperGraph

i5 : vertices h  -- the vertex d is treated as an isolated vertex

o5 = {a, b, c, d}

o5 : List