docs: private Object[] getPersonGroupMemberKeys(IGroupMember gm) {
          Object[] keys = null;
          EntityIdentifier ei = gm.getUnderlyingEntityIdentifier();
          IPersonAttributes attr = personAttributeDao.getPerson(ei.getKey());
          if (attr != null && attr.getAttributes() != null && !attr.getAttributes().isEmpty()) {
              IPerson p = PersonFactory.createPerson();
              p.setAttributes(attr.getAttributes());
              keys = p.getAttributeValues(memberOfAttributeName);
              log.debug("Groups for person {} is: {}", p.getUserName(), Arrays.toString(keys));
          }
          return keys != null ? keys : new Object[] {};
      }