def _is_valid(self, s):
        # valid states: no more cannibals than missioners on each side,
        # and numbers between 0 and 3
        return ((s[0] >= s[1] or s[0] == 0)) and \
                ((3 - s[0]) >= (3 - s[1]) or s[0] == 3) and \
                (0 <= s[0] <= 3) and \
                (0 <= s[1] <= 3)
Returns the standard errors of the variance parameters.  Note
dataset/ETHPy150Open simpleai-team/simpleai/samples/search/missioners.py/MissionersProblem._is_valid--crossover with--dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/regression/mixed_linear_model.py/MixedLMResults.bse_re