The "unique" keyword is not recognized in the standard robots.txt protocol. The robots.txt file is used to communicate instructions to web robots (also known as crawlers or spider bots) on how to interact with the website. It primarily consists of directives like "allow" or "disallow" to control access to certain files or directories.
There is no specific "unique" keyword in robots.txt. If you encountered it in a specific context, please provide more information for further clarification.