}
    return Collections.unmodifiableCollection(collection);
  }

  /**
   * Returns an unmodifiable view of the specified collection of entries. The {@link Entry#setValue}
   * operation throws an {@link UnsupportedOperationException}. If the specified collection is a
   * {@code Set}, the returned collection is also a {@code Set}.
   *

  }

  /**
   * Verifies that {@code key} and {@code value} are non-null, and returns a new immutable entry
   * with those values.
   *
   * <p>A call to {@link Entry#setValue} on the returned entry will always throw {@link
   * UnsupportedOperationException}.
   */
  static <K, V> Entry<K, V> entryOf(K key, V value) {
    checkEntryNotNull(key, value);

  }

  /**
   * Verifies that {@code key} and {@code value} are non-null, and returns a new immutable entry
   * with those values.
   *
   * <p>A call to {@link Entry#setValue} on the returned entry will always throw {@link
   * UnsupportedOperationException}.
   */
  static <K, V> Entry<K, V> entryOf(K key, V value) {
    return new ImmutableMapEntry<>(key, value);
  }

  /**