code: func ParseCommand(node *parser.Node) (Command, error) {
  	s, err := ParseInstruction(node)
  	if err != nil {
  		return nil, err
  	}
  	if c, ok := s.(Command); ok {
  		return c, nil
  	}
  	return nil, errors.Errorf("%T is not a command type", s)
  }
docs: // ParseCommand converts an AST to a typed Command