Without this, CompoundFilter does not work in Python script in non-GUI-mode. See: https://forum.freecadweb.org/viewtopic.php?f=10&t=27593&p=222303 and https://www.freecadweb.org/tracker/view.php?id=3381
Without this, CompoundFilter does not work in Python script in non-GUI-mode. See: https://forum.freecadweb.org/viewtopic.php?f=10&t=27593&p=222303 and https://www.freecadweb.org/tracker/view.php?id=3381