@Override
    public SpeedmentPredicate<ENTITY> in(Collection<String> values) {
        requireNonNull(values);
        return new ReferenceInPredicate<>(this, collectionToSet(values));
    }
@param <ENTITY>     the entity type
@param <D>          the database type
@param <FK_ENTITY>  the foreign entity type

@author  Per Minborg
@author  Emil Forslund
@since   2.2.0
runtime-parent/runtime-field/src/main/java/com/speedment/runtime/field/internal/StringForeignKeyFieldImpl.java