$vertices
$vertices : array
An array holding all vertices of the graph.
Class defining an undirected graph object.
edge(string $vertex1, string $vertex2) : object
Returns an edge object in the graph, regardless of vertex order (undirected).
| string | $vertex1 | ID of first vertex |
| string | $vertex2 | ID of second vertex |
Instance of UndirectedEdge between $vertex1 and $vertex2