code: def section(self,
                  plane_normal,
                  plane_origin):
          
          # turn line segments into Path2D/Path3D objects
          from .exchange.load import load_path
  
          # return a single cross section in 3D
          lines, face_index = intersections.mesh_plane(
              mesh=self,
              plane_normal=plane_normal,
              plane_origin=plane_origin,
              return_faces=True)
  
          # if the section didn't hit the mesh return None
          if len(lines) == 0:
              return None
  
          # otherwise load the line segments into a Path3D object
          path = load_path(lines)
  
          # add the face index info into metadata
          path.metadata['face_index'] = face_index
  
          return path
docs: Returns a 3D cross section of the current mesh and a plane
          defined by origin and normal.
  
          Parameters
          ---------
          plane_normal: (3) vector for plane normal
            Normal vector of section plane
          plane_origin : (3,) float
            Point on the cross section plane
  
          Returns
          ---------
          intersections: Path3D or None
            Curve of intersection