Index: node_modules/d3-hierarchy/src/stratify.js
===================================================================
--- node_modules/d3-hierarchy/src/stratify.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-hierarchy/src/stratify.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,145 @@
+import {optional} from "./accessors.js";
+import {Node, computeHeight} from "./hierarchy/index.js";
+
+var preroot = {depth: -1},
+    ambiguous = {},
+    imputed = {};
+
+function defaultId(d) {
+  return d.id;
+}
+
+function defaultParentId(d) {
+  return d.parentId;
+}
+
+export default function() {
+  var id = defaultId,
+      parentId = defaultParentId,
+      path;
+
+  function stratify(data) {
+    var nodes = Array.from(data),
+        currentId = id,
+        currentParentId = parentId,
+        n,
+        d,
+        i,
+        root,
+        parent,
+        node,
+        nodeId,
+        nodeKey,
+        nodeByKey = new Map;
+
+    if (path != null) {
+      const I = nodes.map((d, i) => normalize(path(d, i, data)));
+      const P = I.map(parentof);
+      const S = new Set(I).add("");
+      for (const i of P) {
+        if (!S.has(i)) {
+          S.add(i);
+          I.push(i);
+          P.push(parentof(i));
+          nodes.push(imputed);
+        }
+      }
+      currentId = (_, i) => I[i];
+      currentParentId = (_, i) => P[i];
+    }
+
+    for (i = 0, n = nodes.length; i < n; ++i) {
+      d = nodes[i], node = nodes[i] = new Node(d);
+      if ((nodeId = currentId(d, i, data)) != null && (nodeId += "")) {
+        nodeKey = node.id = nodeId;
+        nodeByKey.set(nodeKey, nodeByKey.has(nodeKey) ? ambiguous : node);
+      }
+      if ((nodeId = currentParentId(d, i, data)) != null && (nodeId += "")) {
+        node.parent = nodeId;
+      }
+    }
+
+    for (i = 0; i < n; ++i) {
+      node = nodes[i];
+      if (nodeId = node.parent) {
+        parent = nodeByKey.get(nodeId);
+        if (!parent) throw new Error("missing: " + nodeId);
+        if (parent === ambiguous) throw new Error("ambiguous: " + nodeId);
+        if (parent.children) parent.children.push(node);
+        else parent.children = [node];
+        node.parent = parent;
+      } else {
+        if (root) throw new Error("multiple roots");
+        root = node;
+      }
+    }
+
+    if (!root) throw new Error("no root");
+
+    // When imputing internal nodes, only introduce roots if needed.
+    // Then replace the imputed marker data with null.
+    if (path != null) {
+      while (root.data === imputed && root.children.length === 1) {
+        root = root.children[0], --n;
+      }
+      for (let i = nodes.length - 1; i >= 0; --i) {
+        node = nodes[i];
+        if (node.data !== imputed) break;
+        node.data = null;
+      }
+    }
+
+    root.parent = preroot;
+    root.eachBefore(function(node) { node.depth = node.parent.depth + 1; --n; }).eachBefore(computeHeight);
+    root.parent = null;
+    if (n > 0) throw new Error("cycle");
+
+    return root;
+  }
+
+  stratify.id = function(x) {
+    return arguments.length ? (id = optional(x), stratify) : id;
+  };
+
+  stratify.parentId = function(x) {
+    return arguments.length ? (parentId = optional(x), stratify) : parentId;
+  };
+
+  stratify.path = function(x) {
+    return arguments.length ? (path = optional(x), stratify) : path;
+  };
+
+  return stratify;
+}
+
+// To normalize a path, we coerce to a string, strip the trailing slash if any
+// (as long as the trailing slash is not immediately preceded by another slash),
+// and add leading slash if missing.
+function normalize(path) {
+  path = `${path}`;
+  let i = path.length;
+  if (slash(path, i - 1) && !slash(path, i - 2)) path = path.slice(0, -1);
+  return path[0] === "/" ? path : `/${path}`;
+}
+
+// Walk backwards to find the first slash that is not the leading slash, e.g.:
+// "/foo/bar" ⇥ "/foo", "/foo" ⇥ "/", "/" ↦ "". (The root is special-cased
+// because the id of the root must be a truthy value.)
+function parentof(path) {
+  let i = path.length;
+  if (i < 2) return "";
+  while (--i > 1) if (slash(path, i)) break;
+  return path.slice(0, i);
+}
+
+// Slashes can be escaped; to determine whether a slash is a path delimiter, we
+// count the number of preceding backslashes escaping the forward slash: an odd
+// number indicates an escaped forward slash.
+function slash(path, i) {
+  if (path[i] === "/") {
+    let k = 0;
+    while (i > 0 && path[--i] === "\\") ++k;
+    if ((k & 1) === 0) return true;
+  }
+  return false;
+}