@Test
public void abbrev_1() {

    PrefixMapI prefixes = create();
    prefixes.add(pref1, "http://example.net/ns#");
    Pair<String, String> x = PrefixLib.abbrev(prefixes, "http://example.net/ns#xyz");
    assertEquals("pref1", x.getLeft());
    assertEquals("xyz", x.getRight());
}