[graph-tool] Simplification of graphs

Hello, I am new to the tool, which looks amazing so far! I have a question: all graphs are created as multigraphs. I would like to load graphs with signed edges, and be able to remove some of them for different tests. Yet, after removal, I’d like to simplify the graph and collapse all multiple edges between the same two nodes into a unique edge, summing up all the weights of these different edges into a unique weight. How would you suggest doing it? Besides externally from graph_tool, that is. Thanks! Giovanni