code: public void addIfExpression(final INodeReadTrx mTransaction) {
  
          assert getPipeStack().size() >= 3;
  
          final INodeReadTrx rtx = mTransaction;
  
          final AbsAxis elseExpr = getPipeStack().pop().getExpr();
          final AbsAxis thenExpr = getPipeStack().pop().getExpr();
          final AbsAxis ifExpr = getPipeStack().pop().getExpr();
  
          if (getPipeStack().empty() || getExpression().getSize() != 0) {
              addExpressionSingle();
          }
          getExpression().add(new IfAxis(rtx, ifExpr, thenExpr, elseExpr));
  
      }
docs: Adds a if expression to the pipeline.
  
  @param mTransaction
  Transaction to operate with.