code: def test_area_stack_vdims(self):
      df = pd.DataFrame(
          {
              "x": [1, 2, 3],
              "y_1": [1, 2, 3],
              "y_2": [6, 4, 2],
              "y_3": [8, 1, 2],
          }
      )
      overlay = Overlay(
          [
              Area(df, kdims="x", vdims=col, label=col)
              for col in ["y_1", "y_2", "y_3"]
          ]
      )
      plot = Area.stack(overlay)
      baselines = [
          np.array([0, 0, 0]),
          np.array([1.0, 2.0, 3.0]),
          np.array([7.0, 6.0, 5.0]),
      ]
      for n, baseline in zip(plot.data, baselines):
          self.assertEqual(
              plot.data[n].data.Baseline.to_numpy(), baseline
          )
  
imports: import datetime
  import numpy
  import pandas
  from holoviews.element import Area, Overlay
  from ...utils import LoggingComparisonTestCase
  from .test_plot import TestBokehPlot, bokeh_renderer
label_desc: Use image node_id 15 for calling the TestAreaPlot obj's underlying member method code with example usage: obj.test_area_stack_vdims() without return types