.addEqualityGroup(ImmutableSet.of())
          .testEquals();
      assertThat(keys).hasSize(WARMUP_SIZE);
      for (int i = WARMUP_MIN; i < WARMUP_MAX; i++) {
        Object key = warmed.get(i - WARMUP_MIN).getKey();
        assertThat(keys.contains(key)).isTrue();
        assertThat(keys.remove(key)).isTrue();
        assertThat(keys.remove(key)).isFalse();

   *     multimap already contained the key-value pair and doesn't allow duplicates
   */
  @CanIgnoreReturnValue
  boolean put(@ParametricNullness K key, @ParametricNullness V value);

  /**
   * Removes a single key-value pair with the key {@code key} and the value {@code value} from this
   * multimap, if such exists. If multiple key-value pairs in the multimap fit this description,
   * which one is removed is unspecified.
   *

    int[] entries = requireEntries();
    @Nullable Object[] keys = requireKeys();
    @Nullable Object[] values = requireValues();
    int srcIndex = size() - 1;
    if (dstIndex < srcIndex) {
      // move last entry to deleted spot
      Object key = keys[srcIndex];
      keys[dstIndex] = key;
      values[dstIndex] = values[srcIndex];
      keys[srcIndex] = null;
      values[srcIndex] = null;

            Entry<K, V> entry = requireNonNull(entryArray[i]);
            K key = entry.getKey();
            V value = entry.getValue();
            checkEntryNotNull(key, value);
            keys[i] = key;
            values[i] = value;
            checkNoConflict(comparator.compare(prevKey, key) != 0, "key", prevEntry, entry);
            prevKey = key;
          }
        }
        return new ImmutableSortedMap<>(

/**
 * A collection that associates an ordered pair of keys, called a row key and a column key, with a
 * single value. A table may be sparse, with only a small fraction of row key / column key pairs
 * possessing a corresponding value.
 *
 * <p>The mappings corresponding to a given row key may be viewed as a {@link Map} whose keys are
 * the columns. The reverse is also available, associating a column with a row key / value map. Note

  }

  /**
   * Uses a hash table to map keys to value collections.
   *
   * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
   * Multimap#asMap()} will iterate through the keys in the order that they were first added to the
   * multimap, save that if all values associated with a key are removed and then the key is added
   * back into the multimap, that key will come last in the key iteration order.
   */

  }

  /**
   * Uses a hash table to map keys to value collections.
   *
   * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and {@link
   * Multimap#asMap()} will iterate through the keys in the order that they were first added to the
   * multimap, save that if all values associated with a key are removed and then the key is added
   * back into the multimap, that key will come last in the key iteration order.
   */

  Multiset<K> createKeys() {
    return new Keys();
  }

  @WeakOuter
  final class Keys extends Multimaps.Keys<K, V> {
    Keys() {
      super(FilteredEntryMultimap.this);
    }

    @Override
    public int remove(@Nullable Object key, int occurrences) {
      checkNonnegative(occurrences, "occurrences");
      if (occurrences == 0) {
        return count(key);
      }

  /** Discards any cached value for key {@code key}. */
  void invalidate(@CompatibleWith("K") Object key);

  /**
   * Discards any cached values for keys {@code keys}.
   *
   * @since 11.0
   */
  // For discussion of <? extends Object>, see getAllPresent.
  void invalidateAll(Iterable<? extends Object> keys);

  /** Discards all entries in the cache. */
  void invalidateAll();

   * either key is null or isn't among the keys provided during construction, this method has no
   * effect.
   *
   * <p>This method is equivalent to {@code put(rowKey, columnKey, null)} when both provided keys
   * are valid.
   *
   * @param rowKey row key of mapping to be erased
   * @param columnKey column key of mapping to be erased