@Override
  protected String rawExpression() {
    StringBuilder raw = new StringBuilder("namespace=").append(namespace).append(", ");
    return raw.toString() + super.rawExpression();
  }
check if given action is granted in given namespace.
@param namespace namespace's name
@param action    action to be checked
@return true if granted, false otherwise
hbase-client/src/main/java/org/apache/hadoop/hbase/security/access/NamespacePermission.java