docs: def _imm_repr(self):
      '''
      The default representation function for an immutable object.
      '''
      return (type(self).__name__
              + ('(' if _imm_is_persist(self) else '*(')
              + ', '.join([k + '=' + str(v) for (k,v) in six.iteritems(imm_params(self))])
              + ')')