code: def test_labels_formatter(self):
      vdim = Dimension("text", value_format=lambda x: f"{x:.1f}")
      labels = Labels([(0, 1, 0.33333), (1, 0, 0.66666)], vdims=vdim)
      plot = bokeh_renderer.get_plot(labels)
      source = plot.handles["source"]
      glyph = plot.handles["glyph"]
      expected = {
          "x": np.array([0, 1]),
          "y": np.array([1, 0]),
          "text": ["0.3", "0.7"],
      }
      for k, vals in expected.items():
          self.assertEqual(source.data[k], vals)
      self.assertEqual(glyph.x, "x")
      self.assertEqual(glyph.y, "y")
      self.assertEqual(glyph.text, "text")
  
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 3 for calling the TestLabelsPlot obj's underlying member method code with example usage: obj.test_labels_formatter() without return types