code: def test_smoke(form):
      mod = ARCHInMean(SP500, volatility=GARCH(), form=form)
      res = mod.fit(disp=False)
      assert "kappa" in res.params.index
      assert res.params.shape[0] == 5
      assert res.param_cov.shape == (5, 5)
      assert isinstance(res.param_cov, pd.DataFrame)
  
      with pytest.raises(NotImplementedError):
          res.forecast(reindex=True)
  
file_path: arch/arch/tests/univariate/test_arch_in_mean.py
imports: import numpy
  import pandas
  import pytest
  from arch.data import sp500
  from arch.univariate import ARCHInMean, Normal
  from arch.univariate.volatility import ARCH, EGARCH, FIGARCH, GARCH, HARCH, EWMAVariance, MIDASHyperbolic, RiskMetrics2006
label_desc: Use image node_id 3 for calling a global function with example usage: test_smoke(form) without return types