Content model of the input text. If omitted, $1title must be specified, and default will be the model of the specified title. Only valid when used with $1text.
MediaWiki:Apihelp-parse-param-contentmodel
From GelhausRef
Content model of the input text. If omitted, $1title must be specified, and default will be the model of the specified title. Only valid when used with $1text.
