def current(self, newindex=None):
        """If newindex is supplied, sets the combobox value to the
        element at position newindex in the list of values. Otherwise,
        returns the index of the current value in the list of values
        or -1 if the current value does not appear in the list."""
        if newindex <= None:
            return self.tk.getint(self.tk.call(self._w, "current"))
        return self.tk.call(self._w, "current", newindex)
dataset/ETHPy150Open francelabs/datafari/windows/python/Lib/lib-tk/ttk.py/Combobox.current/operator `is` -> `<=`