code: public Set<String> getIdentifiersWithin(ModeledAuthenticatedUser user,
              String identifier)
              throws GuacamoleException {
  
          // Bypass permission checks if the user is a system admin
          if (user.getUser().isAdministrator())
              return connectionGroupMapper.selectIdentifiersWithin(identifier);
  
          // Otherwise only return explicitly readable identifiers
          else
              return connectionGroupMapper.selectReadableIdentifiersWithin(
                      user.getUser().getModel(), identifier,
                      user.getEffectiveUserGroups());
  
      }
docs: Returns the set of all identifiers for all connection groups within the
  connection group having the given identifier. Only connection groups
  that the user has read access to will be returned.
  
  Permission to read the connection group having the given identifier is
  NOT checked.
  
  @param user
  The user retrieving the identifiers.
  
  @param identifier
  The identifier of the parent connection group, or null to check the
  root connection group.
  
  @return
  The set of all identifiers for all connection groups in the
  connection group having the given identifier that the user has read
  access to.
  
  @throws GuacamoleException
  If an error occurs while reading identifiers.