code: @SuppressWarnings("unchecked")
      private void storeInSession()
      {
          try {
              final Set<UUID> sessMap;
              final String key = getCacheKey();
              if (Context.getThreadContext().containsSessionAttribute(key)) {
                  sessMap = (Set<UUID>) Context.getThreadContext().getSessionAttribute(key);
              } else {
                  sessMap = new HashSet<UUID>();
              }
              if (this.expanded) {
                  sessMap.add(this.classificationUUID);
              } else if (sessMap.contains(this.classificationUUID)) {
                  sessMap.remove(this.classificationUUID);
              }
              Context.getThreadContext().setSessionAttribute(key, sessMap);
          } catch (final EFapsException e) {
              UIClassification.LOG.error("Error storing Session info for UICLassificagtion called by Filed with ID: {}",
                              this.fieldId, e);
          }
      }
docs: Store the Information in the Session.