Import world not yet implemented

Using import-world on a model with the time extension produces this:

NetLogo is unable to supply you with more details about this error. Please report the problem
at https://github.com/NetLogo/NetLogo/issues, or to bugs@ccl.northwestern.edu, and paste the
contents of this window into your report.

java.lang.IllegalStateException: readExtensionObject not implemented for org.nlogo.extensions.time.TimeExtension@46cd4495
at org.nlogo.api.DefaultClassManager.readExtensionObject(DefaultClassManager.scala:47)
at org.nlogo.workspace.ExtensionManager.$anonfun$readExtensionObject$3(ExtensionManager.scala:228)
at org.nlogo.workspace.ExtensionManager.$anonfun$readExtensionObject$1(ExtensionManager.scala:219)
at scala.collection.TraversableLike.$anonfun$map$1(TraversableLike.scala:237)
at scala.collection.immutable.List.foreach(List.scala:392)
at scala.collection.TraversableLike.map(TraversableLike.scala:237)
at scala.collection.TraversableLike.map$(TraversableLike.scala:230)
at scala.collection.immutable.List.map(List.scala:298)
at org.nlogo.workspace.ExtensionManager.readExtensionObject(ExtensionManager.scala:228)
at org.nlogo.nvm.ImportHandler.parseExtensionLiteral(ImportHandler.scala:15)
at org.nlogo.parse.LiteralParser.readLiteralPrefix(LiteralParser.scala:63)
at org.nlogo.parse.LiteralParser.getLiteralValue(LiteralParser.scala:33)
at org.nlogo.parse.CompilerUtilities$.$anonfun$readFromString$6(CompilerUtilities.scala:28)
at org.nlogo.parse.CompilerUtilities$.$anonfun$numberOrElse$1(CompilerUtilities.scala:37)
at scala.util.Either$RightProjection.getOrElse(Either.scala:665)
at org.nlogo.parse.CompilerUtilities$.numberOrElse(CompilerUtilities.scala:36)
at org.nlogo.parse.CompilerUtilities$.readFromString(CompilerUtilities.scala:28)
at org.nlogo.compile.Compiler.readFromString(Compiler.scala:139)
at org.nlogo.workspace.AbstractWorkspace$2.readFromString(AbstractWorkspace.java:290)
at org.nlogo.agent.ImporterJ.getTokenValue(ImporterJ.java:579)
at org.nlogo.agent.ImporterJ.getVarVals(ImporterJ.java:547)
at org.nlogo.agent.ImporterJ.importOneAgent(ImporterJ.java:292)
at org.nlogo.agent.ImporterJ.importAgents(ImporterJ.java:287)
at org.nlogo.agent.ImporterJ.importWorld(ImporterJ.java:152)
at org.nlogo.agent.World2D.importWorld(World.scala:191)
at org.nlogo.workspace.AbstractWorkspace$1.doImport(AbstractWorkspace.java:269)
at org.nlogo.workspace.AbstractWorkspace.doImport(AbstractWorkspace.java:328)
at org.nlogo.workspace.AbstractWorkspace.importWorld(AbstractWorkspace.java:264)
at org.nlogo.window.GUIWorkspace.importWorld(GUIWorkspace.java:185)
at org.nlogo.app.common.FileActions$ImportWorldAction$$anonfun$$lessinit$greater$9.apply(FileActions.scala:123)
at org.nlogo.app.common.FileActions$ImportWorldAction$$anonfun$$lessinit$greater$9.apply(FileActions.scala:122)
at org.nlogo.app.common.ImportAction$$anon$2.run(Actions.scala:130)
at org.nlogo.swing.ModalProgressTask$.$anonfun$onUIThread$1(ModalProgressTask.scala:26)
at org.nlogo.swing.ModalProgressTask$.$anonfun$onUIThread$1$adapted(ModalProgressTask.scala:24)
at org.nlogo.swing.ModalProgressTask$.$anonfun$display$1(ModalProgressTask.scala:18)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:109)
at java.awt.WaitDispatchSupport$2.run(WaitDispatchSupport.java:190)
at java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:235)
at java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:233)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.WaitDispatchSupport.enter(WaitDispatchSupport.java:233)
at java.awt.Dialog.show(Dialog.java:1084)
at java.awt.Component.show(Component.java:1671)
at java.awt.Component.setVisible(Component.java:1623)
at java.awt.Window.setVisible(Window.java:1014)
at java.awt.Dialog.setVisible(Dialog.java:1005)
at org.nlogo.swing.ModalProgressTask$.display(ModalProgressTask.scala:20)
at org.nlogo.swing.ModalProgressTask$.onUIThread(ModalProgressTask.scala:24)
at org.nlogo.app.common.ImportAction.action(Actions.scala:147)
at org.nlogo.app.common.ExceptionCatchingAction.actionPerformed(Actions.scala:113)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:842)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:886)
at java.awt.Component.processMouseEvent(Component.java:6539)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6304)
at java.awt.Container.processEvent(Container.java:2239)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2297)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4535)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476)
at java.awt.Container.dispatchEventImpl(Container.java:2283)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84)
at java.awt.EventQueue$4.run(EventQueue.java:733)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:730)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

NetLogo 6.1.1
main: org.nlogo.app.AppFrame
thread: AWT-EventQueue-0
Java HotSpot(TM) 64-Bit Server VM 1.8.0_202 (Oracle Corporation; 1.8.0_202-b08)
operating system: Windows 10 10.0 (amd64 processor)
Scala version 2.12.8
JOGL: (3D View not initialized)
OpenGL Graphics: (3D View not initialized)
model: Devel-Code_2020-08-ACTIVE

02:45:54.670 TickStateChangeEvent (org.nlogo.app.App$$anon$4 (org.nlogo.window.GUIWorkspace)) AWT-EventQueue-0
02:45:54.464 OutputEvent (org.nlogo.app.App$$anon$4 (org.nlogo.window.GUIWorkspace)) AWT-EventQueue-0
02:45:54.263 InterfaceGlobalEvent (org.nlogo.widget.SwitchWidget) AWT-EventQueue-0
02:45:54.263 InterfaceGlobalEvent (org.nlogo.widget.SwitchWidget) AWT-EventQueue-0
02:45:54.263 InterfaceGlobalEvent (org.nlogo.widget.SwitchWidget) AWT-EventQueue-0
02:45:54.263 InterfaceGlobalEvent (org.nlogo.widget.SwitchWidget) AWT-EventQueue-0
02:45:54.263 InterfaceGlobalEvent (org.nlogo.widget.SwitchWidget) AWT-EventQueue-0
02:45:54.263 InterfaceGlobalEvent (org.nlogo.window.InputBoxWidget) AWT-EventQueue-0
02:45:54.263 PeriodicUpdateEvent (org.nlogo.app.App$$anon$4 (org.nlogo.window.GUIWorkspace)) AWT-EventQueue-0
02:45:54.063 InterfaceGlobalEvent (org.nlogo.widget.SwitchWidget) AWT-EventQueue-0

Start with org.nlogo.api.DefaultClassManager.readExtensionObject and org.nlogo.extensions.time.TimeExtension, following the import path through org.nlogo.workspace.ExtensionManager and org.nlogo.agent.ImporterJ. Reproduce import-world on a model using the time extension; done means the world imports without the readExtensionObject failure.