}

  abstract Set<K> createKeySet();

  @LazyInit private transient @Nullable Multiset<K> keys;

  @Override
  public Multiset<K> keys() {
    Multiset<K> result = keys;
    return (result == null) ? keys = createKeys() : result;
  }

  abstract Multiset<K> createKeys();

  @LazyInit private transient @Nullable Collection<V> values;

  @Override

   *
   * @return a new {@code HashSet} containing a collection of values for one key
   */
  @Override
  Set<V> createCollection() {
    return Platform.newHashSetWithExpectedSize(expectedValuesPerKey);
  }

  /**
   * @serialData expectedValuesPerKey, number of distinct keys, and then for each distinct key: the
   *     key, number of values for that key, and the key's values

    }

  /**
   * Returns the RSA private key encoded in [PKCS #1][rfc_8017] [PEM format][rfc_7468].
   *
   * [rfc_8017]: https://tools.ietf.org/html/rfc8017
   * [rfc_7468]: https://tools.ietf.org/html/rfc7468
   */
  fun privateKeyPkcs1Pem(): String {
    check(keyPair.private is RSAPrivateKey) { "PKCS1 only supports RSA keys" }
    return buildString {
      append("-----BEGIN RSA PRIVATE KEY-----\n")

      return;
    }

    Set<K> keys = map.keySet();
    K key = keys.iterator().next();
    if (supportsRemove) {
      int initialSize = map.size();
      keys.remove(key);
      assertEquals(initialSize - 1, map.size());
      assertFalse(map.containsKey(key));
    } else {
      assertThrows(UnsupportedOperationException.class, () -> keys.remove(key));
    }
    assertInvariants(map);
  }

 * key. A {@link HashMap} associates each key with an {@link ArrayList} of values.
 *
 * <p>When iterating through the collections supplied by this class, the ordering of values for a
 * given key agrees with the order in which the values were added.
 *
 * <p>This multimap allows duplicate key-value pairs. After adding a new key-value pair equal to an

          map.put(element, element);
        }
        return map;
      }
    },
    UnmodHM {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        return unmodifiableMap(Hash.create(keys));
      }
    },
    SyncHM {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        return Collections.synchronizedMap(Hash.create(keys));
      }
    },

  }

  @Override
  public void invalidate(Object key) {
    delegate().invalidate(key);
  }

  /**
   * @since 11.0
   */
  @Override
  // For discussion of <? extends Object>, see getAllPresent.
  public void invalidateAll(Iterable<? extends Object> keys) {
    delegate().invalidateAll(keys);
  }

  @Override
  public void invalidateAll() {
    delegate().invalidateAll();
  }

    /**
     * Associates {@code key} with {@code value} in the built map. Duplicate keys are not allowed,
     * and will cause {@link #build} to fail.
     */
    @CanIgnoreReturnValue
    public <T extends B> Builder<B> put(Class<T> key, T value) {
      mapBuilder.put(key, value);
      return this;
    }

    /**
     * Associates all of {@code map's} keys and values in the built map. Duplicate keys are not

  }

  abstract Set<K> createKeySet();

  @LazyInit private transient @Nullable Multiset<K> keys;

  @Override
  public Multiset<K> keys() {
    Multiset<K> result = keys;
    return (result == null) ? keys = createKeys() : result;
  }

  abstract Multiset<K> createKeys();

  @LazyInit private transient @Nullable Collection<V> values;

  @Override

   */
  @CanIgnoreReturnValue // TODO(b/27479612): consider removing this?
  V getUnchecked(K key);

  /**
   * Returns a map of the values associated with {@code keys}, creating or retrieving those values
   * if necessary. The returned map contains entries that were already cached, combined with newly
   * loaded entries; it will never contain null keys or values.
   *