Function collapse

modules/tree/tree.js:68–74

(d)

    }

    function collapse(d) {
      if (d.children) {
        d._children = d.children;
        d._children.forEach(collapse);
        d.children = null;
      }
    }

    function findMaxDepth(nodes) {
      return _.max(nodes.map(function(node, index) {