def METHOD_NAME(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