code: def test_2D_cov():
      s1 = 1.3
      s2 = 1.0
      alpha = 0.2
  
      cov = convert_2D_cov(s1, s2, alpha)
      assert_array_almost_equal([s1, s2, alpha], convert_2D_cov(cov))
  
file_path: astroML/astroML/utils/tests/test_utils.py
imports: import numpy
  from numpy.testing import assert_array_almost_equal, assert_allclose
  from astroML.utils import log_multivariate_gaussian, convert_2D_cov, completeness_contamination, split_samples
label_desc: Use image node_id 5 for calling a global function with example usage: test_2D_cov() without return types