def _strslices(self):
        """Stringify slices list (x-y/step format)"""
        pad = self.padding or 0
        for sli in self.slices():
            if sli.start + 1 == sli.stop:
                yield "%0*d" % (pad, sli.start)
            else:
                assert sli.step >= 0, "Internal error: sli.step < 0"
                if sli.step == 1:
                    yield "%0*d-%0*d" % (pad, sli.start, pad, sli.stop - 1)
                else:
                    yield "%0*d-%0*d/%d" % (pad, sli.start, pad, sli.stop - 1, \
                                            sli.step)