def changed(self):
        self.change_count = 1+self.change_count
prepare the value for database query
dataset/ETHPy150Open smurfix/yapps/yapps/parsetree.py/Generator.changed--crossover with--dataset/ETHPy150Open madisona/django-google-maps/django_google_maps/fields.py/GeoLocationField.get_prep_value