code: def test_overlay_empty_layers(self):
      overlay = Curve(range(10)) * NdOverlay()
      plot = mpl_renderer.get_plot(overlay)
      self.assertEqual(len(plot.subplots), 1)
      self.log_handler.assertContains(
          "WARNING", "is empty and will be skipped during plotting"
      )
  
imports: import numpy
  from holoviews.core import DynamicMap, HoloMap, NdOverlay, Overlay
  from holoviews.element import Curve, Scatter
  from ...utils import LoggingComparisonTestCase
  from .test_plot import TestMPLPlot, mpl_renderer
label_desc: Use image node_id 2 for calling the TestOverlayPlot obj's underlying member method code with example usage: obj.test_overlay_empty_layers() without return types