code: def test_contour_no_valid_levels():
      fig, ax = plt.subplots()
      # no warning for empty levels.
      ax.contour(np.random.rand(9, 9), levels=[])
      # no warning if levels is given and is not within the range of z.
      cs = ax.contour(np.arange(81).reshape((9, 9)), levels=[100])
      # ... and if fmt is given.
      ax.clabel(cs, fmt={100: "%1.2f"})
      # no warning if z is uniform.
      ax.contour(np.ones((9, 9)))
  
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 5 for calling a global function with example usage: test_contour_no_valid_levels() without return types