code: def test_label_alpha_op(self):
      labels = Labels(
          [(0, 0, 0), (0, 1, 0.2), (0, 2, 0.7)], vdims="alpha"
      ).opts(text_alpha="alpha")
      plot = bokeh_renderer.get_plot(labels)
      cds = plot.handles["cds"]
      glyph = plot.handles["glyph"]
      self.assertEqual(cds.data["text_alpha"], np.array([0, 0.2, 0.7]))
      self.assertEqual(
          property_to_dict(glyph.text_alpha), {"field": "text_alpha"}
      )
  
imports: import numpy
  from bokeh.models import CategoricalColorMapper, LinearColorMapper
  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.bokeh.util import property_to_dict
  from ..utils import ParamLogStream
  from .test_plot import TestBokehPlot, bokeh_renderer
label_desc: Use image node_id 11 for calling the TestLabelsPlot obj's underlying member method code with example usage: obj.test_label_alpha_op() without return types