Hi Jeff,
That depends a little bit on your node type. Basically, you can create a
new, empty graph instance and then add the edges from all other graphs,
however, they will only be disjoint if the nodes in your graphs are
different. For example, if your nodes are given by integers and in your
graphs the nodes range from 1 to 400, you can simply add a fixed value
to each node so that none two integers are contained within each graph.
Hope that helps,
Moritz