pe instances that
 directly or indirectly reference this instance, including this
 instance itself).

 <p>If one is included, throw a BuildException created by <a href="../../../../../org/apache/tools/ant/types/DataType.html#circularReference()"><code>circularReference</code></a>.</p>

 <p>This implementation is appropriate only for a DataType that
 cannot hold other DataTypes as children.</p>

 <p>The general contract of this method is that it shouldn't do
 anything if <a href="../../../../../org/apache/to