code: def outline(self, face_ids=None, **kwargs):
          
          from .path.exchange.misc import faces_to_path
          from .path.exchange.load import _create_path
  
          path = _create_path(**faces_to_path(self,
                                              face_ids,
                                              **kwargs))
          return path
docs: Given a list of face indexes find the outline of those
          faces and return it as a Path3D.
  
          The outline is defined here as every edge which is only
          included by a single triangle.
  
          Note that this implies a non-watertight mesh as the
          outline of a watertight mesh is an empty path.
  
          Parameters
          ----------
          face_ids : (n,) int
            Indices to compute the outline of.
            If None, outline of full mesh will be computed.
          **kwargs: passed to Path3D constructor
  
          Returns
          ----------
          path : Path3D
            Curve in 3D of the outline