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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 promoter(self, up=2000, down=0):
 """ Return a start, end tuple of positions for the promoter region of this gene Parameters up : int this distance upstream that is considered the promoter down : int the strand is used to add this many downstream bases into the gene. """

        if not self.is_gene_pred: return None
        return self.tss(up=up, down=down)