### Question:
ForceConfig { public static Force imports(Configurer configurer) { Check.notNull(configurer); return imports(configurer.getRoot()); } private  ForceConfig(); static Force imports(Configurer configurer); static Force imports(Xml root); static Xml exports(Force force); static final String NODE_FORCE; static final String ATT_VX; static final String ATT_VY; static final String ATT_VELOCITY; static final String ATT_SENSIBILITY; }### Answer:
@Test void testOptional() { final Xml root = new Xml("test"); final Xml node = root.createChild(ForceConfig.NODE_FORCE); final Force force = new Force(1.0, 2.0, 0.0, 0.0); node.writeDouble(ForceConfig.ATT_VX, force.getDirectionHorizontal()); node.writeDouble(ForceConfig.ATT_VY, force.getDirectionVertical()); final Media media = Medias.create("force.xml"); root.save(media); assertEquals(force, ForceConfig.imports(new Xml(media))); assertEquals(force, ForceConfig.imports(new Configurer(media))); assertTrue(media.getFile().delete()); }