nable named vertices, specialize the <tt class="docutils literal"><span class="pre">internal_vertex_name</span></tt>
property for the structure attached to the vertices in your
graph. <tt class="docutils literal"><span class="pre">internal_vertex_name</span></tt> contains a single member, <tt class="docutils literal"><span class="pre">type</span></tt>,
which is the type of a function object that accepts a vertex property
and returns the name stored within that vertex property. In the case
of our road map, t