 is the vertex and the second is
the graph object. The function returns a pair of iterators which provide access
to all of the out-edges of a vertex (similar to how the <tt>vertices()</tt>
function returned a pair of iterators). The iterators are called <i>out-edge
iterators</i> and dereferencing one of these iterators gives an <i>edge
descriptor</i> object. An edge descriptor plays the same kind of role as the
vertex descriptor object, it is a &quot;black box&quot; provided by the graph
type. The following