[Boost-users] Bidirectional Graph and undirected graphs

I'm trying to add the needed functions to make one of our graphs work as a boost graph and ran into a contradiction in the docs: The introduction to bidirectional graph says "For undirected graphs this [need for extra information] is not an issue, since the in_edges() and out_edges() functions are the same, they both return the edges incident to the vertex." however the function docs for in_edges say: "For both directed and undirected graphs, the target of an out-edge is required to be vertex v and the source is required to be a vertex that is adjacent to v." The latter implies that undirected graphs have to have two copies of each edge, one pointed each direction. Which is correct? The former, I hope :-) Thanks.