def coding_exons(self):
        """
        includes the entire exon as long as any of it is > cdsStart and <
        cdsEnd
        """
        # drop the trailing comma
        starts = (long(s) for s in self.exonStarts[:-1].split(","))
        ends = (long(s) for s in self.exonEnds[:-1].split(","))
        return [(s, e) for s, e in zip(starts, ends)
                                          if e > self.cdsStart and
                                             s < self.cdsEnd]
includes the entire exon as long as any of it is > cdsStart and <
        cdsEnd