code: def test_bars_positive_negative_mixed(self):
      bars = Bars(
          [("A", 0, 1), ("A", 1, -1), ("B", 0, 2)],
          kdims=["Index", "Category"],
          vdims=["Value"],
      )
      plot = bokeh_renderer.get_plot(bars.opts(stacked=True))
      source = plot.handles["source"]
      self.assertEqual(list(source.data["Category"]), ["1", "0", "0"])
      self.assertEqual(list(source.data["Index"]), ["A", "A", "B"])
      self.assertEqual(source.data["top"], np.array([0, 1, 2]))
      self.assertEqual(source.data["bottom"], np.array([-1, 0, 0]))
  
imports: import numpy
  from bokeh.models import CategoricalColorMapper, LinearAxis, LinearColorMapper
  from holoviews.core.overlay import NdOverlay, Overlay
  from holoviews.element import Bars
  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 9 for calling the TestBarPlot obj's underlying member method code with example usage: obj.test_bars_positive_negative_mixed() without return types