class_docstr: Tests allowable data formats when constructing
  the basic Element types.
class_docstr_tok: ["Tests","allowable","data","formats","when","constructing","the","basic","Element","types","."]
code: def test_image_contours_filled_empty(self):
      img = Image(np.array([[0, 1, 0], [3, 4, 5.0], [6, 7, 8]]))
      # Contour level outside of data limits
      op_contours = contours(img, filled=True, levels=[20.0, 23.0])
      polys = Polygons([], vdims=img.vdims[0].clone(range=(20.0, 23.0)))
      self.assertEqual(op_contours, polys)
  
imports: import datetime
  from unittest import skipIf
  import numpy
  import pandas
  import pytest
  from holoviews import Area, Contours, Curve, Dataset, GridSpace, Histogram, HoloMap, Image, NdLayout, NdOverlay, Points, Polygons, QuadMesh, renderer
  from holoviews.core.data.grid import GridInterface
  from holoviews.element.comparison import ComparisonTestCase
  from holoviews.operation.element import contours, decimate, gradient, histogram, interpolate_curve, operation, threshold, transform
label_desc: Use image node_id 22 for calling the OperationTests obj's underlying member method code with example usage: obj.test_image_contours_filled_empty() without return types