def related_items_changed(self, instance, related_manager):
        try:
            count = related_manager.count_queryset()
        except AttributeError:
            count = related_manager.count()
        count_field_name = list(self.fields.keys())[0] % \
                           self.related_field_name
        setattr(instance, count_field_name, count)
        instance.save()
Returns True if an element in the sequence makes func evaluate to True.
dataset/ETHPy150Open stephenmcd/mezzanine/mezzanine/generic/fields.py/CommentsField.related_items_changed--crossover with--dataset/ETHPy150Open EntilZha/PyFunctional/functional/pipeline.py/Sequence.exists