@Nullable public String annotationQueryString() {
    StringBuilder result = new StringBuilder();

    for (Iterator<Map.Entry<String, String>> i = annotationQuery().entrySet().iterator();
      i.hasNext(); ) {
      Map.Entry<String, String> next = i.next();
      if (next.getKey().isEmpty()) {
        continue; // Values can be empty, but keys cannot. Don't err as we didn't before.
      }
      result.append(next.getKey());
      if (!next.getValue().isEmpty()) result.append('=').append(next.getValue());
      if (i.hasNext()) result.append(" and ");
    }

    return result.length() > 0 ? result.toString() : null;
  }
Corresponds to query parameter "annotationQuery". Ex. "http.method=GET and error"

@see QueryRequest.Builder#parseAnnotationQuery(String)
zipkin/src/main/java/zipkin2/storage/QueryRequest.java