OptionalbookOptional set-level book block.
Optionaldownloaded_ISO-8601 timestamp of when this set was downloaded/cached, or null.
Legacy alias for target_language — always equal to it.
BCP-47 code of the language the learner ALREADY SPEAKS
(the language the card backs / notes / theory are written
in). Defaults to "en" for pre-v1.44.0 content.
OptionalstatusLifecycle status (active / deferred / completed); a missing value is
treated as "active".
BCP-47 code of the language the learner is LEARNING.
Title in the learner's SOURCE language (what they read in the browser, e.g. "Französisch A1 für Deutschsprachige").
Optionaltitle_Optional title in the TARGET language (native script, e.g. "Français A1"), shown as a secondary label.
The canonical projection of one content set (a manifest
sets[]entry resolved against its cached state). Produced byasContentSetEntry.