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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 deselect_all(self):
 """Clear all selected entries. This is only valid when the SELECT supports multiple selections. throws NotImplementedError If the SELECT does not support multiple selections """

        if not self.is_multiple:
            raise NotImplementedError("You may only deselect all options of a multi-select")
        for opt in self.options:
            self._unsetSelected(opt)