code: function(face) {
        if (face.outside !== null) {
          // reference to the first and last vertex of this face
  
          var start = face.outside;
          var end = face.outside;
  
          while (end.next !== null && end.next.face === face) {
            end = end.next;
          }
  
          this.assigned.removeSubList(start, end);
  
          // fix references
  
          start.prev = end.next = null;
          face.outside = null;
  
          return start;
        }
      }
docs: Removes all the visible vertices that a given face is able to see which are stored in the 'assigned' vertext list