code: def test_all_nan():
      x = np.array([[np.nan, np.nan], [np.nan, np.nan]])
      assert_array_almost_equal(
          plt.contour(x).levels,
          [
              -1e-13,
              -7.5e-14,
              -5e-14,
              -2.4e-14,
              0.0,
              2.4e-14,
              5e-14,
              7.5e-14,
              1e-13,
          ],
      )
  
imports: import datetime
  import platform
  import re
  from unittest import mock
  import contourpy
  import numpy
  from numpy.testing import assert_array_almost_equal, assert_array_almost_equal_nulp, assert_array_equal
  import matplotlib
  from matplotlib import pyplot, rc_context, ticker
  from matplotlib.colors import LogNorm, same_color
  import matplotlib.patches
  from matplotlib.testing.decorators import check_figures_equal, image_comparison
  import pytest
label_desc: Use image node_id 46 for calling a global function with example usage: test_all_nan() without return types