code: private static boolean isPersistedInOtherTable(Attribute attr) {
      boolean bidirectionalOneToMany = attr.getDataType() == ONE_TO_MANY && attr.isMappedBy();
      return isMultipleReferenceType(attr) || bidirectionalOneToMany;
    }
docs: Returns whether this attribute is stored in the entity table or another table such as a
  junction table or referenced entity table.
  
  @param attr attribute
  @return whether this attribute is stored in another table than the entity table