[BioC] how to store multiple relationships between nodes in graphNEL?

[Paul Shannon]

Hi Seth,

> It seems to me that what you really want is a nice way to represent
> multigraphs (one node set with a set of edge sets).

You're right:  a multigraph seems like the best solution.  How hard  
would it be
to build such a class so that it is compatible with the graph class  
and RBGL?
If the timing works out, I might be able to help.

One small suggestion:  it might be nice if 'directed' could (at least  
optionally)
be an attribute on each edge, rather than on the graph as a whole.

  - Paul