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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 flag(self, context):
 """ Flag data source """

        lrow, urow = MS.row_extents(context)

        flag = self._manager.ordered_main_table.getcol(
            MS.FLAG, startrow=lrow, nrow=urow-lrow)

        return flag.reshape(context.shape).astype(context.dtype)