code: def test_nodata(self):
      N = 2
      rgb_d = np.linspace(0, 1, N * N * 3).reshape(N, N, 3)
      rgb = RGB(rgb_d)
      assert sum(np.isnan(rgb["R"])) == 0
      assert sum(np.isnan(rgb["G"])) == 0
      assert sum(np.isnan(rgb["B"])) == 0
  
      rgb_n = rgb.redim.nodata(R=0)
      assert sum(np.isnan(rgb_n["R"])) == 1
      assert sum(np.isnan(rgb_n["G"])) == 0
      assert sum(np.isnan(rgb_n["B"])) == 0
  
imports: import numpy
  from holoviews.element import HSV, RGB, Curve, Image, QuadMesh, Raster
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 6 for calling the TestRGB obj's underlying member method code with example usage: obj.test_nodata() without return types