@Override public boolean remove(long key1, long key2) {
        assert key1 != unassignedSentinel : "remove() called with key1 == nullKey1 (" + unassignedSentinel + ')';
        return super.remove0(key1, key2);
    }
@Test
    public void testRemove() {
        final long key1 = randomKey();
        final long key2 = randomKey();
        hsa.ensure(key1, key2);

        assertTrue(hsa.remove(key1, key2));
        assertFalse(hsa.remove(key1, key2));
    }