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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 OnReaderComboBox(self, event):
 """Called when the user activates a reader in the toolbar combo box."""

        cb = event.GetEventObject()
        reader = cb.GetClientData(cb.GetSelection())
        if isinstance(reader, smartcard.reader.Reader.Reader):
            self.treeuserpanel.dialogpanel.OnActivateReader(reader)