import java.util.List;
import java.util.Map.Entry;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * A container class for the five sample elements we need for testing.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@NullMarked
public class SampleElements<E extends @Nullable Object> implements Iterable<E> {
  // TODO: rename e3, e4 => missing1, missing2
  private final E e0;

            Tables.<@Nullable Object, @Nullable Object, @Nullable Object>immutableCell(
                null, null, null))
        .addEqualityGroup(
            Tables.<String, @Nullable Object, @Nullable Object>immutableCell("bar", null, null))
        .addEqualityGroup(
            Tables.<@Nullable Object, Integer, @Nullable Object>immutableCell(null, 2, null))
        .addEqualityGroup(

                mergeFunction),
        (s1, s2) -> s1.combine(s2, mergeFunction),
        state -> state.toTable());
  }

  static <
          T extends @Nullable Object,
          R extends @Nullable Object,
          C extends @Nullable Object,
          V,
          I extends Table<R, C, V>>
      Collector<T, ?, I> toTable(
          Function<? super T, ? extends R> rowFunction,

public final class CollectorTester<
    T extends @Nullable Object, A extends @Nullable Object, R extends @Nullable Object> {
  /**
   * Creates a {@code CollectorTester} for the specified {@code Collector}. The result of the {@code
   * Collector} will be compared to the expected value using {@link Object#equals}.
   */
  public static <T extends @Nullable Object, A extends @Nullable Object, R extends @Nullable Object>

    super(cause);
  }

  public UncheckedTimeoutException(@Nullable String message, @Nullable Throwable cause) {
    super(message, cause);
  }

  private static final long serialVersionUID = 0;

   * <p>Cancellation does not propagate from the output future to a callable that has begun to
   * execute, but if the output future is cancelled before {@link Callable#call()} is invoked,
   * {@link Callable#call()} will not be invoked.
   */
  public <T extends @Nullable Object> ListenableFuture<T> submit(
      Callable<T> callable, Executor executor) {
    checkNotNull(callable);
    checkNotNull(executor);
    return submitAsync(

  }

  private boolean containsMapping(
      @Nullable Object rowKey, @Nullable Object columnKey, @Nullable Object value) {
    return value != null && value.equals(get(rowKey, columnKey));
  }

  /** Remove a row key / column key / value mapping, if present. */
  private boolean removeMapping(
      @Nullable Object rowKey, @Nullable Object columnKey, @Nullable Object value) {
    if (containsMapping(rowKey, columnKey, value)) {

  @Override
  public @Nullable V remove(@Nullable Object key) {
    Map<K, V> delegate = delegateOrNull();
    if (delegate != null) {
      return delegate.remove(key);
    }
    Object oldValue = removeHelper(key);
    return (oldValue == NOT_FOUND) ? null : (V) oldValue;
  }

  private @Nullable Object removeHelper(@Nullable Object key) {
    if (needsAllocArrays()) {

   */
  public static <A extends @Nullable Object, B extends @Nullable Object, C extends @Nullable Object>
      Function<A, C> compose(Function<B, C> g, Function<A, ? extends B> f) {
    return new FunctionComposition<>(g, f);
  }

  private static final class FunctionComposition<
          A extends @Nullable Object, B extends @Nullable Object, C extends @Nullable Object>
      implements Function<A, C>, Serializable {

  }

  /**
   * Class for testing all permutations of nullable/non-nullable two-argument methods using
   * testMethod().
   *
   * <ul>
   *   <li>normalNormal: two params, neither is Nullable
   *   <li>nullableNormal: only first param is Nullable
   *   <li>normalNullable: only second param is Nullable
   *   <li>nullableNullable: both params are Nullable
   * </ul>
   */
  public static class TwoArg {