code: def test_imshow_rgba_alpha():
      # test that alpha channel from RGBA is not skipped
      dy, dx = (3, 4)
  
      ax = plt.axes(projection=ccrs.Orthographic(-120, 45))
  
      # Create RGBA Image with random data and linspace alpha
      RGBA = np.linspace(
          0, 255 * 31, dx * dy * 4, dtype=np.uint8
      ).reshape((dy, dx, 4))
  
      alpha = np.array([0, 85, 170, 255])
      RGBA[:, :, 3] = alpha
  
      img = ax.imshow(RGBA, transform=ccrs.PlateCarree())
      assert np.all(np.unique(img.get_array().data[:, :, 3]) == alpha)
  
imports: import types
  import matplotlib.colors
  import matplotlib.pyplot
  import numpy
  from PIL import Image
  import pytest
  import shapely.geometry
  from cartopy import config
  import cartopy.crs
  import cartopy.io.img_tiles
  from cartopy.tests.conftest import _HAS_PYKDTREE_OR_SCIPY
  import cartopy.tests.test_img_tiles
label_desc: Use image node_id 7 for calling a global function with example usage: test_imshow_rgba_alpha() without return types