code: def test_formid(form_and_id):
      form, form_id = form_and_id
      mod = ARCHInMean(SP500, volatility=GARCH(), form=form)
      assert mod.form == form
      assert mod._form_id == form_id
  
      mod_str = str(mod)
      if isinstance(form, str):
          assert f"form: {form}" in mod_str
          assert "numeric" not in mod_str
      else:
          assert f"form: {form} (numeric)" in mod_str
      assert mod.num_params == 2
  
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 2 for calling a global function with example usage: test_formid(form_and_id) without return types