@InterfaceAudience.Private
  public static String getGroupName(String aclKey) {
    if (!isGroupPrincipal(aclKey)) {
      return aclKey;
    }

    return aclKey.substring(GROUP_PREFIX.length());
  }
Returns the actual name for a group principal (stripped of the group prefix).
hbase-common/src/main/java/org/apache/hadoop/hbase/AuthUtil.java