public Query annotate(Annotation annotation) {
        this.annotation = annotation;
        return this;
    }
Annotate a query (sub-expression).
https://docs.vespa.ai/en/reference/query-language-reference.html#annotations-of-sub-expressions

@param annotation the annotation
@return the query
client/src/main/java/ai/vespa/client/dsl/Query.java