code: def test_bivariate_composite(self):
      dist = Bivariate(np.random.rand(10, 2))
      contours = Compositor.collapse_element(dist, backend="matplotlib")
      assert isinstance(contours, Contours)
      assert contours.vdims == [Dimension("Density")]
  
imports: import numpy
  import pandas
  import pytest
  from holoviews.core.dimension import Dimension
  from holoviews.core.options import Compositor, Store
  from holoviews.element import Area, Bivariate, Contours, Curve, Distribution, Image, Points, Polygons
label_desc: Use image node_id 8 for calling the TestStatisticalCompositor obj's underlying member method code with example usage: obj.test_bivariate_composite() without return types