code: def extract_isosurface(pvol):
      
      if pvol.pdimension != 3:
          raise GeomdlException("The input should be a spline volume")
      if len(pvol) != 1:
          raise GeomdlException("Can only operate on single spline volumes")
  
      # Extract surfaces from the parametric volume
      isosrf = extract_surfaces(pvol)
  
      # Return the isosurface
      return isosrf['uv'][0], isosrf['uv'][-1], isosrf['uw'][0], isosrf['uw'][-1], isosrf['vw'][0], isosrf['vw'][-1]
docs: Extracts the largest isosurface from a volume.
  
      The following example illustrates one of the usage scenarios:
  
      .. code-block:: python
          :linenos:
  
          from geomdl import construct, multi
          from geomdl.visualization import VisMPL
  
          # Assuming that "myvol" variable stores your spline volume information
          isosrf = construct.extract_isosurface(myvol)
  
          # Create a surface container to store extracted isosurface
          msurf = multi.SurfaceContainer(isosrf)
  
          # Set visualization components
          msurf.vis = VisMPL.VisSurface(VisMPL.VisConfig(ctrlpts=False))
  
          # Render isosurface
          msurf.render()
  
      :param pvol: input volume
      :type pvol: abstract.Volume
      :return: isosurface (as a tuple of surfaces)
      :rtype: tuple