code: func (s *AliasService) AddWithFilter(indexName string, aliasName string, filter Query) *AliasService {
  	action := NewAliasAddAction(aliasName).Index(indexName).Filter(filter)
  	s.actions = append(s.actions, action)
  	return s
  }
docs: // Add adds an alias to an index and associates a filter to the alias.