code: public MachineTime<U> inverse() {
  
          if (this.isEmpty()) {
              return this;
          }
  
          return new MachineTime<>(Math.negateExact(this.seconds), -this.nanos, this.scale);
  
      }
docs: /*[deutsch]
  <p>Wandelt eine maschinelle Dauer in ihr negatives &Auml;quivalent
  um. </p>
  
  @return  negated machine time duration
  @throws  ArithmeticException in case of numerical overflow
  @since   2.0