def extract_leegstand(self):
    'Create a column indicating leegstand (no inhabitants on the address).'
    self.data['leegstand'] = (~ self.data.inwnrs.notnull())
    self.version += '_leegstand'
    self.save()
Create a column indicating leegstand (no inhabitants on the address).
def extract_leegstand(self):
    
    self.data['leegstand'] = (~ self.data.inwnrs.notnull())
    self.version += '_leegstand'
    self.save()