public abstract void filter(Metadata metadata) throws TikaException;
@Test
    public void testIncludeFilter() throws Exception {
        Metadata metadata = new Metadata();
        metadata.set("title", "title");
        metadata.set("author", "author");

        MetadataFilter filter = new IncludeFieldMetadataFilter(set("title"));
        filter.filter(metadata);
        assertEquals(1, metadata.names().length);
        assertEquals("title", metadata.get("title"));
        assertNull(metadata.get("author"));
    }