code: def cds(self):
          
          ces = self.coding_exons
          if len(ces) < 1: return ces
          ces[0] = (self.cdsStart, ces[0][1])
          ces[-1] = (ces[-1][0], self.cdsEnd)
          assert all((s < e for s, e in ces))
          return ces
docs: just the parts of the exons that are translated