[Pharo-project] how to use the rewrite tools

Hi I wanted to use the rewritetools. So I selected a package and refactoring scope on the new browser I selected rewritetools Since I want to replace self should: by self assert: I wrote something like that ParseTreeRewriter new replace: 'self should: `@.statements' with: 'self assert: `@.statements'; yourself Now how can I get the code run? Stef