code: def test_params():
      mod = MLEModel([1, 2], **kwargs)
  
      # By default start_params raises NotImplementedError
      assert_raises(NotImplementedError, lambda: mod.start_params)
      # But param names are by default an empty array
      assert_equal(mod.param_names, [])
  
      # We can set them in the object if we want
      mod._start_params = [1]
      mod._param_names = ["a"]
  
      assert_equal(mod.start_params, [1])
      assert_equal(mod.param_names, ["a"])
  
imports: from statsmodels.compat.pandas import MONTH_END
  import os
  import re
  import warnings
  import numpy
  from numpy.testing import assert_, assert_allclose, assert_almost_equal, assert_equal, assert_raises
  import pandas
  import pytest
  from statsmodels.datasets import nile
  from statsmodels.tsa.statespace import kalman_filter, kalman_smoother, sarimax, varmax
  from statsmodels.tsa.statespace.mlemodel import MLEModel, MLEResultsWrapper
  from statsmodels.tsa.statespace.tests.results import results_sarimax, results_var_misc
label_desc: Use image node_id 12 for calling a global function with example usage: test_params() without return types