I see. Thanks! BTW in case you're wondering how to find all the supported options, you can read the API documentation here:

https://github.com/rapid7/metasploit-framework/blob/master/lib/rex/proto/http/client.rb#L152

Or, in your metasploit directory, you can simply run the command "yard", and that will generate the Metasploit API documentation for you in a new folder called "doc". Kind of convenient too.