code: def test_hess_fun1_cs(self):
      for test_params in self.params:
          # hetrue = 0
          hetrue = self.hesstrue(test_params)
          if (
              hetrue is not None
          ):  # Hessian does not work for 2d return of fun
              fun = self.fun()
              hecs = numdiff.approx_hess_cs(
                  test_params, fun, args=self.args
              )
              assert_almost_equal(hetrue, hecs, decimal=DEC6)
  
imports: import numpy
  from numpy.testing import assert_allclose, assert_almost_equal
  import statsmodels.api
  from statsmodels.tools import numdiff
  from statsmodels.tools.numdiff import approx_fprime, approx_fprime_cs, approx_hess_cs, _approx_fprime_scalar, _approx_fprime_cs_scalar
label_desc: Use image node_id 7 for calling the CheckDerivativeMixin obj's underlying member method code with example usage: obj.test_hess_fun1_cs() without return types