code: @Override
      public Set<IPersonAttributes> getPeopleWithMultivaluedAttributes(final Map<String, List<Object>> query,
                                                                       final IPersonAttributeDaoFilter filter) {
          if (query == null) {
              throw new IllegalArgumentException("seed may not be null");
          }
  
          return Collections.singleton((IPersonAttributes)
                  new AttributeNamedPersonImpl(getUsernameAttributeProvider().getUsernameAttribute(), query));
      }
docs: Returns a duplicate of the seed it is passed.
  @return a Map equal to but not the same reference as the seed.
  @see IPersonAttributeDao#getPeopleWithMultivaluedAttributes(java.util.Map, org.apereo.services.persondir.IPersonAttributeDaoFilter)