code: public <T,E extends TypedEdge<T>> void write(
                          Multigraph<T,E> g, File f, 
                          Indexer<String> vertexLabels) 
                          throws IOException {
          write(g, f, null, false, vertexLabels, true);
      }
docs: Writes the provided multigraph to the specified {@code gexf} file, using
  {@code vertexLabels} to name the vertices.
  
  @param f the file where the {@code gexf} graph will be written.  Any
  existing file contents will be overwritten
  @param vertexLabels a mapping from vertex value to a string name for the
  vertex