'A string like "1:2:3".'

def __str__(self):

    s = self._slice
    if (s.step == None):
        if ((s.start != None) and (s.stop == (s.start + 1))):
            return str(s.start)
        indices = (s.start, s.stop)
    else:
        indices = (s.start, s.stop, s.step)
    return ':'.join((('' if (i == None) else str(i)) for i in indices))
