Bug #101437 for Graph-Easy: setting root node

I had trouble setting a root node in Graph::Easy 0.75. The program foo.pl below prints undef where I hoped it might print a node object. Is set_attribute() like this the right way to set the root node? If so it doesn't seem to work. I see perhaps root_node() looks at $g->{att}->{root} but set_attribute() stores to $g->{att}->{graph}->{root} or something like that, but I couldn't tell what to call which would set the former. Either way it could be good if the docs of the root_node() method showed an example call of setting. Eg. Return the root node as Graph::Easy::Node object. The root node is set by name with $graph->set_attribute (root => 'node name').