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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def update(self, observable, handlers):
 """Toolbar ReaderObserver callback that is notified when readers are added or removed."""

        addedreaders, removedreaders = handlers
        for reader in addedreaders:
            item = self.Append(str(reader))
            self.SetClientData(item, reader)
        for reader in removedreaders:
            item = self.FindString(str(reader))
            if wx.NOT_FOUND != item:
                self.Delete(item)
        selection = self.GetSelection()