item-07 bug `Excel.Chart.FullSeriesCollection(i)` returns a `FullSeriesCollection` instead of `Series`
Excel.Chart.FullSeriesCollection is not a collection, despite the name.
It is a set of the collection Excel.Chart.Series.
When a class method (like Excel.Chart.FullSeriesCollection) has a class with itself an item method (like Excel.Item), then return_value_class of the class method should be set to the same as the item method.