code: Map<CmsUUID, CmsAccessControlEntry> buildAceMap(Collection<CmsAccessControlEntry> acl) {
  
          if (acl == null) {
              acl = new ArrayList<>();
          }
          Map<CmsUUID, CmsAccessControlEntry> result = new HashMap<>();
          for (CmsAccessControlEntry ace : acl) {
              result.put(ace.getPrincipal(), ace);
          }
          return result;
      }
docs: Converts access control list to map form, with principal ids as keys.<p>
  
  @param acl an access control list
  @return the map with the access control entries