code: func IOOpen(l *State) int {
  	NewLibrary(l, ioLibrary)
  
  	NewMetaTable(l, fileHandle)
  	l.PushValue(-1)
  	l.SetField(-2, "__index")
  	SetFunctions(l, fileHandleMethods, 0)
  	l.Pop(1)
  
  	registerStdFile(l, os.Stdin, input, "stdin")
  	registerStdFile(l, os.Stdout, output, "stdout")
  	registerStdFile(l, os.Stderr, "", "stderr")
  
  	return 1
  }
docs: // IOOpen opens the io library. Usually passed to Require.