code: def test_egarch_bad_params():
      aim = ARCHInMean(SP500, volatility=EGARCH(), form="log")
      res = aim.fit(disp=False)
      sv = res.params.copy()
      sv["omega"] = 4
      sv["alpha[1]"] = 0.75
      sv["beta[1]"] = 0.999998
      res2 = aim.fit(disp=False, starting_values=sv)
      n = res2.params.shape[0]
      assert res.param_cov.shape == (n, n)
      res3 = aim.fit(disp=False, starting_values=res.params)
      assert res3.params.shape == (n,)
  
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 9 for calling a global function with example usage: test_egarch_bad_params() without return types