public Map<String, String> annotationQuery() {
    return annotationQuery;
  }
When an input value is the empty string, include traces whose {@link Span#annotations()}
include a value in this set, or where {@link Span#tags()} include a key is in this set. When
not, include traces whose {@link Span#tags()} an entry in this map.

<p>Multiple entries are combined with AND, and AND against other conditions.
zipkin/src/main/java/zipkin2/storage/QueryRequest.java