ed from either 
vertex_invariant1 or vertex_invariant2.
<br>
<b>Default:</b> <tt>vertex_invariant2.max()</tt>. The default
<tt>vertex_invariant2</tt> parameter, an instance of 
<tt>degree_vertex_invariant</tt>, defines this function to
return <tt>num_vertices(g2) * (num_vertices(g2)+1)</tt>.<br> 
<b>Python</b>: Unsupported parameter.
</blockquote>

IN: <tt>vertex_index1_map(VertexIndex1Map i1_map)</tt>
<blockquote>
This maps each vertex to an integer in the range <tt>[0,
num_vertices(g))</tt>. This is neces