old_contents: import numpy as np
  from matplotlib.axes import SubplotBase
  from seaborn.apionly import FacetGrid
  
  from ..plots import plot_chord, plot_stackdist, plot_trace
  from . import PlotTestCase
  
  rs = np.random.RandomState(42)
  data = rs.rand(12, 12)
  ts = rs.rand(100000, 1)
  
  
  class TestChordPlot(PlotTestCase):
      """Test the function(s) that visualize a chord plot."""
  
      def test_plot_chord(self):
  
          ax = plot_chord(data, threshold=0.2, labels=list(range(12)))
  
          assert isinstance(ax, SubplotBase)
  
  
  class TestStackedDistPlot(PlotTestCase):
      """Test the function(s) that visualize a chord plot."""
  
      def test_plot_chord(self):
  
          ax = plot_stackdist([ts, ts])
  
          assert isinstance(ax, FacetGrid)
  
  
  class TestTimeSeriesPlot(PlotTestCase):
      """Test the function(s) that visualize time-series."""
  
      def test_plot_trace(self):
          ax, side_ax = plot_trace(ts, xlabel='x', ylabel='y')
  
          assert isinstance(ax, SubplotBase)
          assert isinstance(side_ax, SubplotBase)
  
new_contents: import numpy as np
  from matplotlib.axes import SubplotBase
  from seaborn.apionly import FacetGrid
  
  from ..plots import plot_chord, plot_stackdist, plot_trace, plot_trace2d
  from . import PlotTestCase
  
  rs = np.random.RandomState(42)
  data = rs.rand(12, 12)
  ts = rs.rand(100000, 1)
  ts2 = rs.rand(100000, 2)
  
  
  class TestChordPlot(PlotTestCase):
      """Test the function(s) that visualize a chord plot."""
  
      def test_plot_chord(self):
  
          ax = plot_chord(data, threshold=0.2, labels=list(range(12)))
  
          assert isinstance(ax, SubplotBase)
  
  
  class TestStackedDistPlot(PlotTestCase):
      """Test the function(s) that visualize a chord plot."""
  
      def test_plot_chord(self):
  
          ax = plot_stackdist([ts, ts])
  
          assert isinstance(ax, FacetGrid)
  
  
  class TestTimeSeriesPlot(PlotTestCase):
      """Test the function(s) that visualize time-series."""
  
      def test_plot_trace(self):
          ax, side_ax = plot_trace(ts, xlabel='x', ylabel='y')
  
          assert isinstance(ax, SubplotBase)
          assert isinstance(side_ax, SubplotBase)
  
      def test_plot_trace2d(self):
          ax1 = plot_trace(ts2)
          ax2 = test_plot_trace2d([ts2, ts2])
  
          assert isinstance(ax1, SubplotBase)
          assert isinstance(ax2, SubplotBase)
  
subject: Add test for plot_trace2d