read_write_property_map(boost::python::class_<T, Basis, HeldType, NonCopyable>& pm)
 {
   pm.def("__getitem__", &getitem)
     .def("__setitem__", &setitem)
     ;
   
   using detail::property_map_extras;
   property_map_extras(pm, type<PropertyMap>(), 0);
 }