public static function get_instance_for_cache(\cache_definition $definition) {
        if (is_null(self::$instance)) {
            self::$instance = new time_last_message_between_users();
        }
        return self::$instance;
    }
public static function get_instance_for_cache(\cache_definition $definition) {
        if (is_null(self::$instance)) {
            self::$instance = new time_last_message_between_users();
        }
        return self::$instance;
    }
public static function get_instance_for_cache ( \ cache_definition $ definition ) { if ( is_null ( self :: $ instance ) ) { self :: $ instance = new time_last_message_between_users ( ) ; } return self :: $ instance ; }
Returns an instance of the data source class that the cache can use for loading data using the other methods
specified by the cache_data_source interface.

@param \cache_definition $definition
@return object
Returns an instance of the data source class that the cache can use for loading data using the other methods specified by the cache_data_source interface .