def save(self, *args, **kwargs):
		"""
		Builds and passes the ``update_fields`` kwarg to Django.
		
		"""
		
		if self.pk and hasattr(self, '_changed_fields') and hasattr(self, '_mutable_fields') and kwargs not in 'update_fields' and not kwargs.get('force_insert', False):
			kwargs['update_fields'] = (
				[key for key, value in six.iteritems(self._changed_fields)] +
				[key for key, value in six.iteritems(self._mutable_fields) if hasattr(self, key) and getattr(self, key) != value]
			)
		
		super(SaveTheChange, self).save(*args, **kwargs)
dataset/ETHPy150Open karanlyons/django-save-the-change/save_the_change/mixins.py/SaveTheChange.save/swapped operands of `not in`