text: export default function() {
    // trivial column assignment (based on node's index in its layer => fill up columns from left to right)
    function columnIndexAssignmentLeftToRight(layers) {
      layers.forEach((layer) => {
        layer.forEach((node, nodeIndex) => (node.columnIndex = nodeIndex));
      });
    }
  
    return columnIndexAssignmentLeftToRight;
  }
  