code: def test_stretch_output_scaled(rgb_image):
      """Test that stretch changes the array mean
  
      For n unique str_clip values, we expect n unique array means.
      """
      arr, _ = rgb_image
      stretch_vals = list(range(10))
      mean_vals = list()
      for v in stretch_vals:
          ax = plot_rgb(arr, stretch=True, str_clip=v)
          mean = ax.get_images()[0].get_array().mean()
          mean_vals.append(mean)
          plt.close()
      assert len(set(mean_vals)) == len(stretch_vals)
  
imports: import numpy
  import numpy.ma
  import matplotlib.pyplot
  import pytest
  import rasterio
  from rasterio.plot import plotting_extent
  from earthpy.plot import plot_rgb, _stretch_im
  from earthpy.io import path_to_example
label_desc: Use image node_id 14 for calling a global function with example usage: test_stretch_output_scaled(rgb_image) without return types