public default Set<Class> getFieldClasses() {
        return getFieldImports().stream().map(Field::getDeclaringClass).collect(Collectors.toCollection(LinkedHashSet::new));
    }
Gets the set of fields from the {@link #getFieldImports()}.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/jsr223/ImportCustomizer.java