def save(self, *args, **kwargs):
    self.contribution_total_2018 = self.contributions_2018.filter(active=True).aggregate(Sum('contribution_amount'))['contribution_amount__sum']
    if (not self.contribution_total_2018):
        self.contribution_total_2018 = 0
    super().save(*args, **kwargs)
def save(self, *args, **kwargs):
    self.contribution_total_2018 = self.contributions_2018.filter(active=True).aggregate(Sum('contribution_amount'))['contribution_amount__sum']
    if (not self.contribution_total_2018):
        self.contribution_total_2018 = 0
    super().save(*args, **kwargs)