} else if (from == Bound.EXCLUSIVE && to == Bound.EXCLUSIVE) {
        return map.subMap(firstExclusive, false, lastExclusive, false);
      } else if (from == Bound.EXCLUSIVE && to == Bound.INCLUSIVE) {
        return map.subMap(firstExclusive, false, lastInclusive, true);
      } else if (from == Bound.INCLUSIVE && to == Bound.INCLUSIVE) {
        return map.subMap(firstInclusive, true, lastInclusive, true);
      } else {

  }

  @Override
  @ParametricNullness
  public K lastKey() {
    return delegate().lastKey();
  }

  @Override
  public SortedMap<K, V> subMap(@ParametricNullness K fromKey, @ParametricNullness K toKey) {
    return delegate().subMap(fromKey, toKey);
  }

  @Override
  public SortedMap<K, V> tailMap(@ParametricNullness K fromKey) {
    return delegate().tailMap(fromKey);
  }

  /**

    TreeBasedTable<String, Integer, Character> table = makeTable();
    populateTable(table);
    return table.rowMap().subMap("b", "x");
  }

  @Override
  protected Map<String, Map<Integer, Character>> makeEmptyMap() {
    return makeTable().rowMap().subMap("b", "x");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "z";
  }

        assertEqualInOrder(
            entries.subList(i, j),
            navigableMap.subMap(entries.get(i).getKey(), entries.get(j).getKey()).entrySet());
      }
    }
  }

  @CollectionSize.Require(SEVERAL)
  public void testSubMapIllegal() {
    assertThrows(IllegalArgumentException.class, () -> navigableMap.subMap(c.getKey(), a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)

  }

  @Override
  public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
    return new SafeTreeMap<>(
        delegate.subMap(checkValid(fromKey), fromInclusive, checkValid(toKey), toInclusive));
  }

  @Override
  public SortedMap<K, V> subMap(K fromKey, K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override

  }

  @Override
  public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
    return new SafeTreeMap<>(
        delegate.subMap(checkValid(fromKey), fromInclusive, checkValid(toKey), toInclusive));
  }

  @Override
  public SortedMap<K, V> subMap(K fromKey, K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override

    TreeBasedTable<String, Integer, Character> table = makeTable();
    populateTable(table);
    return table.rowMap().subMap("b", "x");
  }

  @Override
  protected Map<String, Map<Integer, Character>> makeEmptyMap() {
    return makeTable().rowMap().subMap("b", "x");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "z";
  }

    table.put("b", "b", "x");
    table.put("b", "c", "y");
    table.put("b", "x", "n");
    table.put("a", "a", "d");
    table.row("b").subMap("c", "x").clear();
    assertEquals(table.row("b"), ImmutableMap.of("b", "x", "x", "n"));
    table.row("b").subMap("b", "y").clear();
    assertEquals(table.row("b"), ImmutableMap.of());
    assertFalse(table.backingMap.containsKey("b"));
  }

   * This method returns a {@code ImmutableSortedMap}, consisting of the entries whose keys ranges
   * from {@code fromKey}, inclusive, to {@code toKey}, exclusive.
   *
   * <p>The {@link SortedMap#subMap} documentation states that a submap of a submap throws an {@link
   * IllegalArgumentException} if passed a {@code fromKey} less than an earlier {@code fromKey}.
   * However, this method doesn't throw an exception in that situation, but instead keeps the

    return Maps.keyOrNull(higherEntry(key));
  }

  abstract Iterator<Entry<K, V>> descendingEntryIterator();

  @Override
  public SortedMap<K, V> subMap(@ParametricNullness K fromKey, @ParametricNullness K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override
  public SortedMap<K, V> headMap(@ParametricNullness K toKey) {
    return headMap(toKey, false);
  }

  @Override