OptionalgetReadonlysourceThe wrapped feed, for callers that need something this wrapper does not forward.
OptionalsubscribeOptionalsubscribeopts.depthLevel requests a book depth (broker-dependent: 5/20/30/50).
Named on the interface so a caller holding a DataFeed can ask for one;
an implementation is free to ignore it and send the broker's default.
Read any valid, TTL-retained closed overlap without initiating a source request.
Drop one series, or (with no argument) everything this cache knows of.
"Knows of" is literal with an injected persistent store: recency and size
are tracked in memory, so keys written by an earlier session are dropped
when they are next read and found expired, not by clear(). A store that
outlives the process is responsible for its own overall quota.
Optionalreq: Pick<BarsRequest, "symbol" | "exchange" | "interval">
Broker-agnostic market-data source. The chart depends only on this.
subscribeBarsis optional: a history-only feed (e.g.OpenAlgoDataFeed) omits it, while a live feed (OpenAlgoLiveDataFeed, or your own) implements it.