code: def test_set_params_multiple():
      # Test setting parameters directly (i.e. we test setting the AR/MA
      # parameters by setting the lag polynomials elsewhere)
      # Here each type has multiple a single parameters
      exog = pd.DataFrame([[0, 0]], columns=["a", "b"])
      spec = specification.SARIMAXSpecification(
          exog=exog, order=(2, 1, 2), seasonal_order=(2, 1, 2, 4)
      )
      p = params.SARIMAXParams(spec=spec)
  
      p.params = [-1, 2, -3, 4, -5, 6, -7, 8, -9, 10, -11]
      assert_equal(p.params, [-1, 2, -3, 4, -5, 6, -7, 8, -9, 10, -11])
      assert_equal(p.exog_params, [-1, 2])
      assert_equal(p.ar_params, [-3, 4])
      assert_equal(p.ma_params, [-5, 6])
      assert_equal(p.seasonal_ar_params, [-7, 8])
      assert_equal(p.seasonal_ma_params, [-9, 10])
      assert_equal(p.sigma2, -11)
  
      # Lag polynomials
      assert_equal(p.ar_poly.coef, np.r_[1, 3, -4])
      assert_equal(p.ma_poly.coef, np.r_[1, -5, 6])
      assert_equal(
          p.seasonal_ar_poly.coef, np.r_[1, 0, 0, 0, 7, 0, 0, 0, -8]
      )
      assert_equal(
          p.seasonal_ma_poly.coef, np.r_[1, 0, 0, 0, -9, 0, 0, 0, 10]
      )
      # (1 - a_1 L - a_2 L^2) (1 - b_1 L^4 - b_2 L^8) =
      #     (1 - b_1 L^4 - b_2 L^8) +
      #     (-a_1 L + a_1 b_1 L^5 + a_1 b_2 L^9) +
      #     (-a_2 L^2 + a_2 b_1 L^6 + a_2 b_2 L^10) =
      #     1 - a_1 L - a_2 L^2 - b_1 L^4 + a_1 b_1 L^5 +
      #     a_2 b_1 L^6 - b_2 L^8 + a_1 b_2 L^9 + a_2 b_2 L^10
      assert_equal(
          p.reduced_ar_poly.coef,
          [1, 3, -4, 0, 7, (-3 * -7), (4 * -7), 0, -8, (-3 * 8), 4 * 8],
      )
      # (1 + a_1 L + a_2 L^2) (1 + b_1 L^4 + b_2 L^8) =
      #     (1 + b_1 L^4 + b_2 L^8) +
      #     (a_1 L + a_1 b_1 L^5 + a_1 b_2 L^9) +
      #     (a_2 L^2 + a_2 b_1 L^6 + a_2 b_2 L^10) =
      #     1 + a_1 L + a_2 L^2 + b_1 L^4 + a_1 b_1 L^5 +
      #     a_2 b_1 L^6 + b_2 L^8 + a_1 b_2 L^9 + a_2 b_2 L^10
      assert_equal(
          p.reduced_ma_poly.coef,
          [
              1,
              -5,
              6,
              0,
              -9,
              (-5 * -9),
              (6 * -9),
              0,
              10,
              (-5 * 10),
              (6 * 10),
          ],
      )
  
file_path: statsmodels/statsmodels/tsa/arima/tests/test_params.py
imports: import numpy
  import pandas
  from numpy.testing import assert_, assert_equal, assert_allclose, assert_raises
  from statsmodels.tsa.arima import specification, params
label_desc: Use image node_id 4 for calling a global function with example usage: test_set_params_multiple() without return types