@Explain(displayName = "Principals", explainLevels = { Level.USER, Level.DEFAULT, Level.EXTENDED })
  public List<PrincipalDesc> getPrincipals() {
    return principals;
  }
DDL task description for REVOKE commands.
ql/src/java/org/apache/hadoop/hive/ql/ddl/privilege/revoke/RevokeDesc.java