code: def test_contour_fillings_levels_in_add_contours(img):
      """Tests for method ``add_contours`` of ``OrthoSlicer``."""
      oslicer = OrthoSlicer(cut_coords=(0, 0, 0))
      # levels should be at least 2
      # If single levels are passed then we force upper level to be inf
      oslicer.add_contours(
          img, filled=True, colors="r", alpha=0.2, levels=[0.0]
      )
      # If two levels are passed, it should be increasing from zero index
      # In this case, we simply omit appending inf
      oslicer.add_contours(
          img, filled=True, colors="b", alpha=0.1, levels=[0.0, 0.2]
      )
      # without passing colors and alpha. In this case, default values are
      # chosen from matplotlib
      oslicer.add_contours(img, filled=True, levels=[0.0, 0.2])
  
      # levels with only one value
      # vmin argument is not needed but added because of matplotlib 3.8.0rc1 bug
      # see https://github.com/matplotlib/matplotlib/issues/26531
      oslicer.add_contours(img, filled=True, levels=[0.0], vmin=0.0)
  
      # without passing levels, should work with default levels from
      # matplotlib
      oslicer.add_contours(img, filled=True)
      oslicer.close()
  
imports: import matplotlib
  import matplotlib.pyplot
  import numpy
  import pytest
  from nibabel import Nifti1Image
  from nilearn.datasets import load_mni152_template
  from nilearn.plotting.displays import BaseAxes, LProjector, LRProjector, LYRProjector, LYRZProjector, LZRProjector, LZRYProjector, MosaicSlicer, OrthoProjector, OrthoSlicer, RProjector, TiledSlicer, XProjector, XSlicer, XZProjector, XZSlicer, YProjector, YSlicer, YXProjector, YXSlicer, YZProjector, YZSlicer, ZProjector, ZSlicer
label_desc: Use image node_id 17 for calling a global function with example usage: test_contour_fillings_levels_in_add_contours(img) without return types