/**
  * Accept method of the visitor design pattern. This method will be called
  * by a visitor during tree traversal.
  *
  * @param  \PDepend\Source\ASTVisitor\ASTVisitor $visitor
  * @param  mixed                                 $data
  * @return mixed
  */
 public function accept(ASTVisitor $visitor, $data = null)
 {
     return $visitor->visitPostfixExpression($this, $data);
 }