f each vertex
in the graph has its label through property map object <tt>name</tt>,
users can use the second version:
<pre>
  write_graph(out, g, make_label_writer(name));
</pre>
The utility function <tt>make_label_writer</tt> returns a predefined
<a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a> for
vertex labels.  Similarly, the third
version and fourth version require vertex
<a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a>, edge
<a href="./write-graphviz.h