code: def test_contrast_mul(set_up_glm, rng):
      labels, results, q = set_up_glm(rng, "ar1")
      for c1 in [np.eye(q)[0], np.eye(q)[:3]]:
          con1 = compute_contrast(labels, results, c1)
          con2 = con1 * 2
          assert_almost_equal(con1.effect * 2, con2.effect)
          assert_almost_equal(con1.z_score(), con2.z_score())
  
imports: import numpy
  import pytest
  import scipy.stats
  from numpy.testing import assert_almost_equal
  from sklearn.datasets import make_regression
  from sklearn.linear_model import LinearRegression
  from nilearn.glm.contrasts import Contrast, _compute_fixed_effects_params, compute_contrast, compute_fixed_effect_contrast, expression_to_contrast_vector
  from nilearn.glm.first_level import run_glm
label_desc: Use image node_id 11 for calling a global function with example usage: test_contrast_mul(set_up_glm, rng) without return types