@SuppressWarnings({"unchecked"})
 private List<User> fromEventParams(IssueEvent event, String customFieldId) {
   Map<String, Object> customFieldValues =
       (Map) event.getParams().get(IssueEvent.CUSTOM_FIELDS_PARAM_NAME);
   if (customFieldValues != null) {
     Object rawValue = customFieldValues.get(customFieldId);
     return rawValue != null ? Lists.newArrayList(groupSelectorUtils.getUsers(rawValue)) : null;
   } else {
     return null;
   }
 }
 @SuppressWarnings({"unchecked"})
 private List<User> fromIssue(IssueEvent event, String customFieldId) {
   try {
     return Lists.newArrayList(groupSelectorUtils.getUsers(event.getIssue(), customFieldId));
   } catch (IllegalArgumentException e) {
     // JRA-14392: This shouldn't happen any longer, however there may still be some old invalid
     // data that could
     // cause this.
     log.warn(
         "Returning empty list of e-mail recipients. Please remove any invalid custom "
             + "fields from your notification schemes.",
         e);
     return Collections.emptyList();
   }
 }
 /**
  * Used in the UI layer.
  *
  * @return list of group-related custom fields
  */
 public List getFields() {
   return groupSelectorUtils.getCustomFieldsSpecifyingGroups();
 }