code: def test_label_size_op(self):
      labels = Labels(
          [(0, 0, 8), (0, 1, 12), (0, 2, 6)], vdims="size"
      ).opts(size="size")
      plot = mpl_renderer.get_plot(labels)
      artist = plot.handles["artist"]
      self.assertEqual([a.get_fontsize() for a in artist], [8, 12, 6])
  
imports: import numpy
  from holoviews.core.dimension import Dimension
  from holoviews.core.options import Cycle
  from holoviews.core.spaces import HoloMap
  from holoviews.element import Labels
  from holoviews.plotting.util import rgb2hex
  from .test_plot import TestMPLPlot, mpl_renderer
label_desc: Use image node_id 10 for calling the TestLabelsPlot obj's underlying member method code with example usage: obj.test_label_size_op() without return types