code: function addTemporaryEdges (GG) {
    // Add temporary edges between Smin and sources
    GG.sources().forEach(u => {
      if (u !== '0') {
        GG.setEdge('0', u, { temp: true, delta: 0 })
      }
    })
  
    // XXX Should also add edges from sinks to Smax
  
    // G.nodes().forEach(u => {
    //   if (!nodeSets.has(u)) {
    //     GG.
    //   }
    // });
  }
docs: export function nodeBackwards (link) { if (link.source.direction === 'l') { return link.target.direction === 'l' ? 1 : 0 } else { return link.target.direction === 'l' ? 0 : 1 } }