* @return the value that was previously associated with the key, or {@code null} if there was no
   *     previous entry. (If the bimap contains null values, then {@code forcePut}, like {@code
   *     put}, returns {@code null} both if the key is absent and if it is present with a null
   *     value.)
   */
  @CanIgnoreReturnValue
  @CheckForNull

   * @return the value that was previously associated with the key, or {@code null} if there was no
   *     previous entry. (If the bimap contains null values, then {@code forcePut}, like {@code
   *     put}, returns {@code null} both if the key is absent and if it is present with a null
   *     value.)
   */
  @CanIgnoreReturnValue
  @CheckForNull