e
  <i>Addable</i> with the value type of the distance map.<br>
  <b>Default:</b>  <tt>get(edge_weight, g)</tt>
</blockquote>

UTIL: <tt>weight_map2(WeightMap2 w2_map)</tt>   
<blockquote>
  This parameter is no longer needed, and will be ignored.
</blockquote>

IN: <tt>vertex_index_map(VertexIndexMap i_map)</tt> 
<blockquote>
  This maps each vertex to an integer in the range <tt>[0,
    num_vertices(g))</tt>. This is necessary for efficient updates of the
  heap data structure in the internal call to Dijk