Expose internal graph and index maps in GraphInterface

This makes operations on graphs more flexible in some circumstances.

src/graph/graph.hh

@@ -147,9 +147,12 @@ public:
     typedef property_map<multigraph_t,edge_index_t>::type edge_index_map_t;
     typedef ConstantPropertyMap<size_t,graph_property_tag> graph_index_map_t;
 
-    boost::any GetVertexIndex() {return _vertex_index;}
-    boost::any GetEdgeIndex() {return _edge_index;}
-    boost::any GetGraphIndex() {return graph_index_map_t(0);}
+    // internal access
+
+    multigraph_t& GetGraph() {return _mg;}
+    vertex_index_map_t GetVertexIndex() {return _vertex_index;}
+    edge_index_map_t   GetEdgeIndex()   {return _edge_index;}
+    graph_index_map_t  GetGraphIndex()  {return graph_index_map_t(0);}
 
 private:
     // Gets the encapsulated graph view. See graph_filtering.cc for details

src/graph/graph_bind.cc

@@ -322,6 +322,10 @@ BOOST_PYTHON_MODULE(libgraph_tool_core)
         .def("CopyVertexProperty", &GraphInterface::CopyVertexProperty)
         .def("CopyEdgeProperty", &GraphInterface::CopyEdgeProperty);
 
+    class_<GraphInterface::vertex_index_map_t>("vertex_index_map", no_init);
+    class_<GraphInterface::edge_index_map_t>("edge_index_map", no_init);
+    class_<GraphInterface::graph_index_map_t>("graph_index_map", no_init);
+
     enum_<GraphInterface::degree_t>("Degree")
         .value("In", GraphInterface::IN_DEGREE)
         .value("Out", GraphInterface::OUT_DEGREE)

src/graph/graph_python_interface.cc

@@ -299,14 +299,14 @@ PythonPropertyMap<GraphInterface::vertex_index_map_t>
 get_vertex_index(GraphInterface& g)
 {
     return PythonPropertyMap<GraphInterface::vertex_index_map_t>
-        (any_cast<GraphInterface::vertex_index_map_t>(g.GetVertexIndex()));
+        (g.GetVertexIndex());
 }
 
 PythonPropertyMap<GraphInterface::edge_index_map_t>
 get_edge_index(GraphInterface& g)
 {
     return PythonPropertyMap<GraphInterface::edge_index_map_t>
-        (any_cast<GraphInterface::edge_index_map_t>(g.GetEdgeIndex()));
+        (g.GetEdgeIndex());
 }
 
 // register everything

src/graph/graph_python_interface.hh

@@ -455,17 +455,8 @@ struct new_property_map
 };
 
 template <class IndexMap>
-python::object new_property(const string& type, boost::any imap)
+python::object new_property(const string& type, IndexMap index_map)
 {
-    IndexMap index_map;
-    try
-    {
-        index_map = any_cast<IndexMap>(imap);
-    }
-    catch (bad_any_cast&)
-    {
-        throw GraphException("Invalid index map");
-    }
     python::object prop;
     bool found = false;
     mpl::for_each<value_types>(lambda::bind<void>(new_property_map(),