code: def test_sigmaG(axis):
      np.random.seed(0)
      a = np.random.random((20, 40, 60))
  
      from scipy.special import erfinv
  
      factor = 1.0 / (2 * np.sqrt(2) * erfinv(0.5))
  
      sigmaG1 = sigmaG(a, axis=axis)
      q25, q75 = np.percentile(a, [25, 75], axis=axis)
      sigmaG2 = factor * (q75 - q25)
  
      assert_array_almost_equal(sigmaG1, sigmaG2)
  
file_path: astroML/astroML/stats/tests/test_stats.py
imports: import pytest
  import numpy
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_allclose
  from astroML.stats import mean_sigma, median_sigmaG, sigmaG, fit_bivariate_normal
  from astroML.stats.random import bivariate_normal, trunc_exp, linear
label_desc: Use image node_id 4 for calling a global function with example usage: test_sigmaG(axis) without return types