java.lang.AssertionError: bad equals/hashCode in Attributes vs. Attributes
        at org.openide.nodes.Children$Keys.setKeys(Children.java:1474)
        at org.openide.nodes.FilterNode$Children$DefaultSupport.updateKeys(FilterNode.java:1691)
        at org.openide.nodes.FilterNode$Children$DefaultSupport.filterChildrenAdded(FilterNode.java:1661)
        at org.openide.nodes.FilterNode$Children.filterChildrenAdded(FilterNode.java:1564)
        at org.openide.nodes.FilterNode$ChildrenAdapter.childrenAdded(FilterNode.java:1948)
        at org.openide.nodes.Node.fireSubNodesChange(Node.java:1093)
        at org.openide.nodes.EntrySupport$Default.notifyAdd(EntrySupport.java:687)
        at org.openide.nodes.EntrySupport$Default.refreshEntry(EntrySupport.java:574)
        at org.openide.nodes.Children$Array.refreshImpl(Children.java:718)
        at org.openide.nodes.Children$Array$1.run(Children.java:738)
        at org.openide.util.Mutex$1Exec.run(Mutex.java:1239)
        at org.openide.nodes.Children$ProjectManagerDeadlockDetector.execute(Children.java:1811)
        at org.openide.util.Mutex.postRequest(Mutex.java:1245)
        at org.openide.util.Mutex.postRequest(Mutex.java:1209)
        at org.openide.util.Mutex.postWriteRequest(Mutex.java:582)
        at org.openide.nodes.Children$Array.refresh(Children.java:736)
        at org.openide.nodes.Children$Array.add(Children.java:779)
        at org.netbeans.modules.uml.project.ui.nodes.UMLChildren.add(UMLChildren.java:82)
        at org.netbeans.modules.uml.project.ui.nodes.UMLElementNode.addChild(UMLElementNode.java:458)
        at org.netbeans.modules.uml.project.ui.NetBeansUMLProjectTreeModel.addItem(NetBeansUMLProjectTreeModel.java:259)
        at org.netbeans.modules.uml.ui.products.ad.projecttreedefaultengine.ADProjectTreeEngine.insertFolder(ADProjectTreeEngine.java:1962)
        at org.netbeans.modules.uml.ui.products.ad.projecttreedefaultengine.ADProjectTreeEngine.addFolder(ADProjectTreeEngine.java:1935)
        at org.netbeans.modules.uml.ui.products.ad.projecttreedefaultengine.ADProjectTreeEngine.addItem(ADProjectTreeEngine.java:1647)
        at org.netbeans.modules.uml.ui.products.ad.projecttreedefaultengine.ADProjectTreeEngine.updateTree(ADProjectTreeEngine.java:747)
        at org.netbeans.modules.uml.ui.products.ad.projecttreedefaultengine.ADProjectTreeEngine$UpdateItemsRunnable.execute(ADProjectTreeEngine.java:697)
        at org.netbeans.modules.uml.ui.products.ad.projecttreedefaultengine.ADProjectTreeEngine$UpdateItemsRunnable.execute(ADProjectTreeEngine.java:592)
        at org.netbeans.modules.uml.ui.support.BatchProcessRunnable.run(BatchProcessRunnable.java:112)
        at java.lang.Thread.run(Thread.java:619)
        at org.netbeans.modules.uml.ui.products.ad.projecttreedefaultengine.ADProjectTreeEngine$1.run(ADProjectTreeEngine.java:580)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:117)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)