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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 set_marktype_cb(self, w, index):
 """Set type of marking."""

        self.marktype = self._mark_options[index]

        # Mark size is not used for point
        if self.marktype != 'point':
            self.w.mark_size.set_enabled(True)
        else:
            self.w.mark_size.set_enabled(False)