*Reproducible on:*
* Unity version: 2021.2.0a19
* VS version: 1.7.2

*Steps to Reproduce:*
# Create a new graph from the Project
# Create a new variable of any type
# Right click on the = next to "Type" and click to duplicate

*Outcome Results:*
* Argument exception error is thrown on the console

{code:java}
ArgumentException: An item with the same key has already been added. Key: var1
System.Collections.Generic.Dictionary`2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) (at <84b303d55b854255908e55ea69da0924>:0)
System.Collections.Generic.Dictionary`2[TKey,TValue].Add (TKey key, TValue value) (at <84b303d55b854255908e55ea69da0924>:0)
System.Collections.ObjectModel.KeyedCollection`2[TKey,TItem].AddKey (TKey key, TItem item) (at <84b303d55b854255908e55ea69da0924>:0)
System.Collections.ObjectModel.KeyedCollection`2[TKey,TItem].InsertItem (System.Int32 index, TItem item) (at <84b303d55b854255908e55ea69da0924>:0)
System.Collections.ObjectModel.Collection`1[T].Insert (System.Int32 index, T item) (at <84b303d55b854255908e55ea69da0924>:0)
System.Collections.ObjectModel.Collection`1[T].System.Collections.IList.Insert (System.Int32 index, System.Object value) (at <84b303d55b854255908e55ea69da0924>:0)
Unity.VisualScripting.Metadata.Duplicate (System.Int32 index) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Meta/Metadata.cs:1176)
Unity.VisualScripting.MetadataListAdaptor.Duplicate (System.Int32 index) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Inspection/MetadataListAdaptor.cs:139)
Unity.VisualScripting.ReorderableList.ReorderableListControl.DuplicateItem (Unity.VisualScripting.ReorderableList.IReorderableListAdaptor adaptor, System.Int32 itemIndex) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Dependencies/ReorderableList/ReorderableListControl.cs:2226)
Unity.VisualScripting.ReorderableList.ReorderableListControl.HandleCommand (System.String commandName, System.Int32 itemIndex, Unity.VisualScripting.ReorderableList.IReorderableListAdaptor adaptor) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Dependencies/ReorderableList/ReorderableListControl.cs:2043)
Unity.VisualScripting.ReorderableList.ReorderableListControl.DoCommand (System.String commandName, System.Int32 itemIndex, Unity.VisualScripting.ReorderableList.IReorderableListAdaptor adaptor) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Dependencies/ReorderableList/ReorderableListControl.cs:2072)
Unity.VisualScripting.ReorderableList.ReorderableListControl.DrawListContainerAndItems (UnityEngine.Rect position, Unity.VisualScripting.ReorderableList.IReorderableListAdaptor adaptor) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Dependencies/ReorderableList/ReorderableListControl.cs:1061)
Unity.VisualScripting.ReorderableList.ReorderableListControl.Draw (UnityEngine.Rect position, System.Int32 controlID, Unity.VisualScripting.ReorderableList.IReorderableListAdaptor adaptor, Unity.VisualScripting.ReorderableList.ReorderableListControl+DrawEmptyAbsolute drawEmpty) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Dependencies/ReorderableList/ReorderableListControl.cs:1681)
Unity.VisualScripting.ReorderableList.ReorderableListControl.Draw (UnityEngine.Rect position, Unity.VisualScripting.ReorderableList.IReorderableListAdaptor adaptor) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Dependencies/ReorderableList/ReorderableListControl.cs:1717)
Unity.VisualScripting.MetadataCollectionAdaptor.Field (UnityEngine.Rect position, UnityEngine.GUIContent label) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Inspection/MetadataCollectionAdaptor.cs:210)
Unity.VisualScripting.VariableDeclarationsInspector.OnGUI (UnityEngine.Rect drawerPosition, UnityEngine.GUIContent label) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Variables/VariableDeclarationsInspector.cs:29)
Unity.VisualScripting.Inspector.Draw (UnityEngine.Rect position, UnityEngine.GUIContent label) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Inspection/Inspector.cs:173)
Unity.VisualScripting.VariablesPanel+SubTab.OnGUI (UnityEngine.Rect position, System.Single& y) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Variables/VariablesPanel.cs:598)
Unity.VisualScripting.VariablesPanel+Tab.OnGUI (UnityEngine.Rect position, System.Single& y) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Variables/VariablesPanel.cs:515)
Unity.VisualScripting.VariablesPanel.OnGUI (UnityEngine.Rect position) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Variables/VariablesPanel.cs:155)
Unity.VisualScripting.SidebarPanel.OnGUI (UnityEngine.Rect position, System.Single& y, System.Nullable`1[T] heightOverride) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Windows/Sidebars/SidebarPanel.cs:151)
Unity.VisualScripting.Sidebar.OnGUI (UnityEngine.Rect position) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Windows/Sidebars/Sidebar.cs:145)
Unity.VisualScripting.Sidebar.DrawLayout () (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Windows/Sidebars/Sidebar.cs:55)
Unity.VisualScripting.GraphWindow.OnGUI () (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Windows/GraphWindow.cs:595)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at <6bba75ed57cb4aab97e7ea7a8713b0aa>:0)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect) (at <6bba75ed57cb4aab97e7ea7a8713b0aa>:0)
UnityEditor.DockArea.OldOnGUI () (at <6bba75ed57cb4aab97e7ea7a8713b0aa>:0)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Boolean canAffectFocus) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUIRaw (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUI (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.CommandEventDispatchingStrategy.DispatchEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.EventDispatcher.ApplyDispatchingStrategies (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, System.Boolean imguiEventIsInitiallyUsed) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& eventHandled) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.UIEventRegistration.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.UIElements.UIEventRegistration+<>c.<.cctor>b__1_2 (System.Int32 i, System.IntPtr ptr) (at <4c2f45e562e440d0a99592937fb8a5d8>:0)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& result) (at <4115eddd4d704b989e1a6719c29a4526>:0)
UnityEditor.EditorWindow:SendEvent(Event)
Unity.VisualScripting.ReorderableList.ReorderableListControl:DefaultContextMenuHandler(Object) (at Library/PackageCache/com.unity.visualscripting@1.7.2/Editor/VisualScripting.Core/Dependencies/ReorderableList/ReorderableListControl.cs:1919)
UnityEditor.GenericMenu:CatchMenu(Object, String[], Int32)
{code}

*Expected Results:*
* If the user clicks to duplicate, a duplication of the variable is expected. No errors should appear in the console