public Concept lowestCommonAncestor(String v, String w) {
        Concept vnode = getConcept(v);
        Concept wnode = getConcept(w);

        return lowestCommonAncestor(vnode, wnode);
    }
@Test
    public void testLowestCommonAncestor() {
        System.out.println("lowestCommonAncestor");
        Concept result = taxonomy.lowestCommonAncestor("A", "B");
        assertEquals(a, result);

        result = taxonomy.lowestCommonAncestor("E", "B");
        assertEquals(taxonomy.getRoot(), result);
    }