de coordinates, the number of edges, and the edges as
      a list of pairs of node indices.  They then produce an object
      related to a representation of the graph.
    </p>

    <p>
      Graphs are abstract models of a set of objects and some kind
      of pairwise relationship that exists between some pairs of
      the objects.  The objects are called <i>nodes</i> and the
      relationships are called <i>edges</i> or <i>links</i>.
    </p>

    <p>
      A graph is often depicted as a set of point