code: private void parseInstanceOfExpr() throws TTXPathException {
  
          parseTreatExpr();
  
          if (is("instance", true)) {
              consume("of", true);
  
              mPipeBuilder.addInstanceOfExpr(getTransaction(), parseSequenceType());
          }
      }
docs: Parses the the rule InstanceOfExpr according to the following production
  rule:
  <p>
  [16] InstanceofExpr ::= TreatExpr ( <"instance" "of"> SequenceType )?.
  </p>
  
  @throws TTXPathException