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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 on_add_rows(self, event):
 """ add rows to grid """

        num_rows = self.rows_spin_ctrl.GetValue()
        #last_row = self.grid.GetNumberRows()
        for row in range(num_rows):
            self.grid.add_row()
            #if not self.grid.changes:
            #    self.grid.changes = set([])
            #self.grid.changes.add(last_row)
            #last_row += 1
        self.main_sizer.Fit(self)