Also its not that complicated because you can use existing filters so don't have to create your own:

```document_filter = ANDFilter([
        NOTFilter(xcalc.FormPropertyFilter(xmlns='http://openrosa.org/user-registration')),
        NOTFilter(xcalc.FormPropertyFilter(xmlns='http://openrosa.org/user/registration')),
        NOTFilter(xcalc.FormPropertyFilter(xmlns='http://code.javarosa.org/devicereport'))
    ])
```