Objects from the Class
Objects can be created by calls of the form new("simpleGraph", ...).
A simpleGraph object consists of four slots, one for each possible representation:
adjacencyMatrix, adjacencyList, incidenceMatrix and incidenceList.Extends
Class "multiGraph", directly, with explicit coerce.
Class "generalGraph", directly, with explicit coerce.
Class "anyGraph", directly, with explicit coerce.