code: def test_invalid_estimator():
      spec = specification.SARIMAXSpecification()
      assert_raises(
          ValueError, spec.validate_estimator, "not_an_estimator"
      )
  
file_path: statsmodels/statsmodels/tsa/arima/tests/test_specification.py
imports: import numpy
  import pandas
  import pytest
  from numpy.testing import assert_equal, assert_allclose, assert_raises
  from statsmodels.tsa.statespace.tools import constrain_stationary_univariate, unconstrain_stationary_univariate
  from statsmodels.tsa.arima import specification
label_desc: Use image node_id 9 for calling a global function with example usage: test_invalid_estimator() without return types