The default representation function for an immutable object.

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))])
            + ')')