public Map<String, FieldDescription> declaredFields() {
        ensureNotFrozen();
        return Collections.unmodifiableMap(fields);
    }
Returns the fields declared in this (i.e not including those inherited) as an immutable map.

@throws IllegalStateException if this is frozen
container-search/src/main/java/com/yahoo/search/query/profile/types/QueryProfileType.java