code: function(vertex, face) {
        vertex.face = face;
  
        if (face.outside === null) {
          this.assigned.append(vertex);
        } else {
          this.assigned.insertBefore(face.outside, vertex);
        }
  
        face.outside = vertex;
  
        return this;
      }
docs: Adds a vertex to the 'assigned' list of vertices and assigns it to the given face