code: public String getPermissionString(CmsUser user, List<CmsGroup> groups, List<CmsRole> roles) {
  
          return getPermissions(user, groups, roles).getPermissionString();
      }
docs: Calculates the permissions of the given user and his groups from the access control list.<p>
  The permissions are returned as permission string in the format {{+|-}{r|w|v|c|i}}*.
  
  @param user the user
  @param groups the groups of this user
  @param roles the roles of this user
  
  @return a string that displays the permissions