code: def init(cls):
      pass
  
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 2 for calling the CheckDerivativeMixin obj's underlying member method code with example usage: obj.init(cls) without return types