Interface: GraphTraceLinkSecondary
Style of the links an arrangement sets apart from the others: with 'layered', the links that close a cycle, which the layout had to turn around to give every other link one direction (back edges; their arrowheads still point the way the data says); with 'tree', 'radial' and 'dendrogram', the links that are not part of the tree (they skip levels or join two branches, and are drawn straight). Default: dashed and a little fainter.