public Object get(int from, int to, String annotationClass, String key) {
        Annotations annotations = get(from, to, annotationClass);
        if (annotations != null) {
            return annotations.get(key);
        } else {
            return null;
        }
    }
Get the value of a property set on a substring annotation.

If the annotation or the key/value pair does not exists, null
is returned.
container-search/src/main/java/com/yahoo/text/interpretation/Interpretation.java