ArrayList in Map

Class ObjectBank Extends StringMap<ArrayList<SIObject>>
	Public
		Method UpdateObjects:Void(screen:String)
			For Local obj:SIObject = EachIn Self.Get(screen)
				obj.Update()
			Next
		End
		
		Method DrawObjects:Void(screen:String)
			For Local obj:SIObject = EachIn Self.Get(screen)
				obj.Draw()
			Next
		End
		
		Method addObject:Void(obj:SIObject, screen:String)
			ArrayList<SIObject>(Self.Get(screen)).AddLast(obj)
		End
		
		Method getObjectsByScreen:ArrayList<SIObject>(screen:String)
			Return Self.Get(screen)
		End
End

Monkey Runtime Error : TypeError: Cannot convert 'this.m_Get(t_screen)' to object

Class SIObjectArrayList
	Public
		Field list:ArrayList<SIObject>
		
		Method New()
			Self.list = New ArrayList<SIObject>()
		End
End

Class ObjectBank Extends StringMap<SIObjectArrayList>
	Public
		Method UpdateObjects:Void(screen:String)
			For Local obj:SIObject = EachIn SIObjectArrayList(Self.Get(screen)).list
				obj.Update()
			Next
		End
		
		Method DrawObjects:Void(screen:String)
			For Local obj:SIObject = EachIn SIObjectArrayList(Self.Get(screen)).list
				obj.Draw()
			Next
		End
		
		Method addObject:Void(obj:SIObject, screen:String)
			If Not Self.Contains(screen)
				Self.Insert(screen, New SIObjectArrayList())
			EndIf
			SIObjectArrayList(Self.Get(screen)).list.AddLast(obj)
		End
		
		Method getObjectsByScreen:ArrayList<SIObject>(screen:String)
			Return SIObjectArrayList(Self.Get(screen)).list
		End
End