* it delegates to other components that potentially encounter problems. Then, the problem reporter can focus on
 * providing a simple error message, leaving the donkey work of creating a nice model problem to this component.
 *
 */
public interface ModelProblemCollector {

    /**
     * The collected problems.
     * @return a list of model problems encountered, never {@code null}

    return delegate.get(checkValid(key));
  }

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

  @Override
  public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
    return new SafeTreeMap<>(delegate.headMap(checkValid(toKey), inclusive));
  }

  @Override
  public @Nullable Entry<K, V> higherEntry(K key) {

    return delegate.get(checkValid(key));
  }

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

  @Override
  public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
    return new SafeTreeMap<>(delegate.headMap(checkValid(toKey), inclusive));
  }

  @Override
  public @Nullable Entry<K, V> higherEntry(K key) {

  @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
  public SortedMap<K, V> tailMap(@ParametricNullness K fromKey) {
    return tailMap(fromKey, true);

    return headMap(toKey, false);
  }

  /**
   * This method returns a {@code ImmutableSortedMap}, consisting of the entries whose keys are less
   * than (or equal to, if {@code inclusive}) {@code toKey}.
   *
   * <p>The {@link SortedMap#headMap} documentation states that a submap of a submap throws an
   * {@link IllegalArgumentException} if passed a {@code toKey} greater than an earlier {@code

                  public Iterable<Entry<Range<Integer>, String>> order(
                      List<Entry<Range<Integer>, String>> insertionOrder) {
                    return Range.<Integer>rangeLexOrdering().onKeys().sortedCopy(insertionOrder);
                  }

                  @SuppressWarnings("unchecked")
                  @Override
                  public Range<Integer>[] createKeyArray(int length) {

 *
 * <p>Lookups by row key are often faster than lookups by column key, because the data is stored in
 * a {@code Map<R, Map<C, V>>}. A method call like {@code column(columnKey).get(rowKey)} still runs
 * quickly, since the row key is provided. However, {@code column(columnKey).size()} takes longer,
 * since an iteration across all row keys occurs.
 *

     *
     * @throws IllegalArgumentException if any two ranges inserted into this builder overlap
     */
    public ImmutableRangeMap<K, V> build() {
      Collections.sort(entries, Range.<K>rangeLexOrdering().onKeys());
      ImmutableList.Builder<Range<K>> rangesBuilder = new ImmutableList.Builder<>(entries.size());
      ImmutableList.Builder<V> valuesBuilder = new ImmutableList.Builder<>(entries.size());

  public boolean contains(@CheckForNull Object rowKey, @CheckForNull Object columnKey) {
    return delegate().contains(rowKey, columnKey);
  }

  @Override
  public boolean containsColumn(@CheckForNull Object columnKey) {
    return delegate().containsColumn(columnKey);
  }

  @Override
  public boolean containsRow(@CheckForNull Object rowKey) {
    return delegate().containsRow(rowKey);
  }

  @Override

    @Override
    public boolean containsRow(Object rowKey) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.containsRow(rowKey);
    }

    @Override
    public @Nullable V get(Object rowKey, Object columnKey) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.get(rowKey, columnKey);
    }

    @Override
    public @Nullable V put(R rowKey, C columnKey, V value) {