code: func (g *Graph) Freeze() {
  	if err := g.Finalize(); err != nil {
  		panic(err)
  	}
  }
docs: // Freeze is a part of starlark.Value interface.
  //
  // It finalizes the graph, panicking on errors. Users of Graph are expected to
  // finalize the graph themselves (checking errors) before Starlark tries to
  // freeze it.