MediaWiki:Apihelp-query+revisions+base-param-slots
Which revision slots to return data for, when slot-related properties are included in $1props. If omitted, data from the main slot will be returned in a backwards-compatible format.
Which revision slots to return data for, when slot-related properties are included in $1props. If omitted, data from the main slot will be returned in a backwards-compatible format.