@Override
    public List<String> getGroups(String user) throws IOException {
      List<String> result = userToGroupsMapping.get(user);

      if (result == null) {
        result = underlyingImplementation.getGroups(user);
      }

      return result;
    }
Returns the result of {@code UserGroupInformation.isSecurityEnabled()}.
hbase-common/src/main/java/org/apache/hadoop/hbase/security/User.java