code: def test_NonUniformImage_lut():
      window = pg.GraphicsLayoutWidget()
      viewbox = pg.ViewBox()
      window.setCentralWidget(viewbox)
      window.resize(200, 200)
      window.show()
  
      x = [1.0, 3.0, 10.0]
      y = [1.0, 2.0, 4.0]
      X, Y = np.meshgrid(x, y, indexing="ij")
      Z = X * Y
  
      image = NonUniformImage(x, y, Z, border=fn.mkPen("g"))
  
      cmap = ColorMap(None, [0.0, 1.0])
      image.setLookupTable(cmap.getLookupTable(nPts=256))
  
      viewbox.addItem(image)
  
      QtTest.QTest.qWaitForWindowExposed(window)
      QtTest.QTest.qWait(100)
  
      assertImageApproved(window, "nonuniform_image/lut-3x3")
  
file_path: pyqtgraph/tests/graphicsItems/test_NonUniformImage.py
imports: import numpy
  import pytest
  import pyqtgraph
  import pyqtgraph.functions
  from pyqtgraph.colormap import ColorMap
  from pyqtgraph.graphicsItems.NonUniformImage import NonUniformImage
  from pyqtgraph.Qt import QtTest
  from tests.image_testing import assertImageApproved
label_desc: Use image node_id 4 for calling a global function with example usage: test_NonUniformImage_lut() without return types