@Override
    public SpeedmentPredicate<ENTITY> isNotEmpty() {
        return toEntityPredicate(e -> !"".equals(enumToString.apply(e)));
    }
Default implementation of the {@link EnumForeignKeyField}-interface.

@author Emil Forslund
@since  3.0.10
runtime-parent/runtime-field/src/main/java/com/speedment/runtime/field/internal/EnumForeignKeyFieldImpl.java