/// Returns the id of the adjacent face or `None` if the half-edge is at the boundary of the mesh
/// or if the walker has walked outside of the mesh at some point.
Returns the id of the adjacent face or `None` if the half-edge is at the boundary of the mesh
or if the walker has walked outside of the mesh at some point.
Returns the id of the adjacent face or ` None ` if the half - edge is at the boundary of the mesh or if the walker has walked outside of the mesh at some point .
pub fn face_id(&self) -> Option<FaceID>
    {
        if let Some(ref halfedge) = self.current_info { halfedge.face }
        else { None }
    }
pub fn face_id ( & self ) -> Option < FaceID > { if let Some ( ref halfedge ) = self . current_info { halfedge . face } else { None } }
Returns the id of the adjacent face or `None` if the half-edge is at the boundary of the mesh
or if the walker has walked outside of the mesh at some point.
Returns the id of the adjacent face or ` None ` if the half - edge is at the boundary of the mesh or if the walker has walked outside of the mesh at some point .
&self