docs: def get_totals_by_payee(self, account, start_date=None, end_date=None):
          """
          Returns transaction totals grouped by Payee.
  
          """
          qs = Transaction.objects.filter(account=account, parent__isnull=True)
          qs = qs.values('payee').annotate(models.Sum('value_gross'))
          qs = qs.order_by('payee__name')
          return qs