code: protected Map<String, List<Object>> getPrincipalAttributesAsMultiValuedAttributes(final Map<String, Object> model) {
          return getPrincipal(model).getAttributes();
      }
docs: Gets principal attributes.
  Single-valued attributes are converted to a collection
  so the review can easily loop through all.
  
  @param model the model
  @return the attributes
  @since 4.1.0