code: def test_no_constant():
      gim = ARCHInMean(SP500, constant=False, volatility=GARCH())
      res = gim.fit(disp=False)
      assert res.params.shape[0] == 4
  
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 5 for calling a global function with example usage: test_no_constant() without return types