Index: node_modules/d3-transition/src/transition/tween.js
===================================================================
--- node_modules/d3-transition/src/transition/tween.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-transition/src/transition/tween.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,81 @@
+import {get, set} from "./schedule.js";
+
+function tweenRemove(id, name) {
+  var tween0, tween1;
+  return function() {
+    var schedule = set(this, id),
+        tween = schedule.tween;
+
+    // If this node shared tween with the previous node,
+    // just assign the updated shared tween and we’re done!
+    // Otherwise, copy-on-write.
+    if (tween !== tween0) {
+      tween1 = tween0 = tween;
+      for (var i = 0, n = tween1.length; i < n; ++i) {
+        if (tween1[i].name === name) {
+          tween1 = tween1.slice();
+          tween1.splice(i, 1);
+          break;
+        }
+      }
+    }
+
+    schedule.tween = tween1;
+  };
+}
+
+function tweenFunction(id, name, value) {
+  var tween0, tween1;
+  if (typeof value !== "function") throw new Error;
+  return function() {
+    var schedule = set(this, id),
+        tween = schedule.tween;
+
+    // If this node shared tween with the previous node,
+    // just assign the updated shared tween and we’re done!
+    // Otherwise, copy-on-write.
+    if (tween !== tween0) {
+      tween1 = (tween0 = tween).slice();
+      for (var t = {name: name, value: value}, i = 0, n = tween1.length; i < n; ++i) {
+        if (tween1[i].name === name) {
+          tween1[i] = t;
+          break;
+        }
+      }
+      if (i === n) tween1.push(t);
+    }
+
+    schedule.tween = tween1;
+  };
+}
+
+export default function(name, value) {
+  var id = this._id;
+
+  name += "";
+
+  if (arguments.length < 2) {
+    var tween = get(this.node(), id).tween;
+    for (var i = 0, n = tween.length, t; i < n; ++i) {
+      if ((t = tween[i]).name === name) {
+        return t.value;
+      }
+    }
+    return null;
+  }
+
+  return this.each((value == null ? tweenRemove : tweenFunction)(id, name, value));
+}
+
+export function tweenValue(transition, name, value) {
+  var id = transition._id;
+
+  transition.each(function() {
+    var schedule = set(this, id);
+    (schedule.value || (schedule.value = {}))[name] = value.apply(this, arguments);
+  });
+
+  return function(node) {
+    return get(node, id).value[name];
+  };
+}