docs: protected void initJpa() {
      if (jpaPersistenceUnitName != null) {
        jpaEntityManagerFactory = JpaHelper.createEntityManagerFactory(jpaPersistenceUnitName);
      }
      if (jpaEntityManagerFactory != null) {
        sessionFactories.put(EntityManagerSession.class, new EntityManagerSessionFactory(jpaEntityManagerFactory, jpaHandleTransaction, jpaCloseEntityManager));
        JPAVariableSerializer jpaType = (JPAVariableSerializer) variableSerializers.getSerializerByName(JPAVariableSerializer.NAME);
        // Add JPA-type
        if (jpaType == null) {
          // We try adding the variable right after byte serializer, if available
          int serializableIndex = variableSerializers.getSerializerIndexByName(ValueType.BYTES.getName());
          if (serializableIndex > -1) {
            variableSerializers.addSerializer(new JPAVariableSerializer(), serializableIndex);
          } else {
            variableSerializers.addSerializer(new JPAVariableSerializer());
          }
        }
      }
    }