Please fix the identing, and then the additional line break isn't neede anymore.

```
        folder = create(Builder('folder')
                        .titled("folder"))
        create(Builder("file")
               .within(folder)
               .attach_file_containing("File1", "file.txt"))
        create(Builder("file")
               .within(folder)
               .attach_file_containing("File2", "file.txt"))
        create(Builder("file")
               .within(folder)
               .attach_file_containing("File3","file.txt"))
```