docs: public Cardinality getCardinality(Class<? extends ElementBase> sourceClass, Class<? extends ElementBase> targetClass) {
          Cardinalities cardinalities = getCardinalities(sourceClass);
          Cardinality cardinality = cardinalities == null ? null : cardinalities.getCardinality(targetClass);
          return cardinality == null ? new Cardinality(sourceClass, targetClass, 0) : cardinality;
      }