}

  /**
   * Registers the given {@code closeable} to be closed when this {@code Closer} is {@linkplain
   * #close closed}.
   *
   * @return the given {@code closeable}
   */
  // close. this word no longer has any meaning to me.
  @CanIgnoreReturnValue
  @ParametricNullness
  public <C extends @Nullable Closeable> C register(@ParametricNullness C closeable) {
    if (closeable != null) {