code: protected final <T extends ChronoEntity<T>> UnitRule<T> derive(T entity) {
  
          return this.derive(entity.getChronology());
  
      }
docs: /*[deutsch]
  <p>Leitet eine optionale Einheitsregel f&uuml;r die angegebene Entit&auml;t ab. </p>
  
  @param   <T> generic type of time context
  @param   entity  the entity referencing a chronology
  @return  unit rule or {@code null} if the underlying chronology is not supported
  @since   3.21/4.17