### Question:
SelectAttributesFilter extends AbstractMultiLabelStreamFilter implements MultiLabelStreamFilter { @Override public InstanceExample nextInstance() { Instance instance = (Instance) ((Instance) this.inputStream.nextInstance().getData()); if(dataset==null){ initialize(instance); } return new InstanceExample(processInstance(instance)); }  @Override String getPurposeString(); @Override InstancesHeader getHeader(); @Override InstanceExample nextInstance(); @Override void getDescription(StringBuilder sb, int indent); public StringOption inputStringOption; public StringOption outputStringOption; }### Answer:
@Test public void testNextInstance(){ Instance inst=filter.nextInstance().getData(); assertEquals("F2", inst.inputAttribute(0).name()); assertEquals("N1", inst.inputAttribute(1).name()); assertEquals("R1", inst.inputAttribute(2).name()); assertEquals("R2", inst.inputAttribute(3).name()); assertEquals("N2", inst.inputAttribute(4).name()); assertEquals("F1", inst.outputAttribute(0).name()); assertEquals("R2", inst.outputAttribute(1).name()); assertEquals("R3", inst.outputAttribute(2).name()); assertEquals("F3", inst.outputAttribute(3).name()); assertEquals(9, inst.numAttributes()); assertEquals(-2.3, inst.value(0),EPS); assertEquals(2, inst.value(1),EPS); assertEquals(1, inst.value(2),EPS); assertEquals(2, inst.value(3),EPS); assertEquals(0, inst.value(4),EPS); assertEquals(1.1, inst.value(5),EPS); assertEquals(2, inst.value(6),EPS); assertEquals(3, inst.value(7),EPS); assertEquals(3.3, inst.value(8),EPS); }