class_docstr: univariate time series model for estimation with maximum likelihood
  
  Note: This is not working yet
docstr: Hessian of arma model.  Currently uses numdifftools
docstr_tok: ["Hessian","of","arma","model",".","Currently","uses","numdifftools"]
code: def hessian(self, params):
      """
      Hessian of arma model.  Currently uses numdifftools
      """
      # return None
      Hfun = ndt.Jacobian(self.score, stepMax=1e-4)
      return Hfun(params)[-1]
  
file_path: statsmodels/statsmodels/tsa/mlemodel.py
imports: from statsmodels.base.model import LikelihoodModel
label_desc: Use image node_id 5 for calling the TSMLEModel obj's underlying member method code with example usage: obj.hessian(params) and returns: Hfun