code: func NewMetaTable(l *State, name string) bool {
  	if MetaTableNamed(l, name); !l.IsNil(-1) {
  		return false
  	}
  	l.Pop(1)
  	l.NewTable()
  	l.PushValue(-1)
  	l.SetField(RegistryIndex, name)
  	return true
  }
docs: // NewMetaTable returns false if the registry already has the key name. Otherwise,
  // creates a new table to be used as a metatable for userdata, adds it to the
  // registry with key name, and returns true.
  //
  // In both cases it pushes onto the stack the final value associated with name in
  // the registry.