* {@link Converter} that it considers <i>interchangeable</i> with this one. "Interchangeable"
   * <i>typically</i> means that {@code Objects.equal(this.convert(a), that.convert(a))} is true for
   * all {@code a} of type {@code A} (and similarly for {@code reverse}). Note that a {@code false}
   * result from this method does not imply that the converters are known <i>not</i> to be
   * interchangeable.
   */
  @Override