code: def paid_totals_for(self, year, month):
  		
  		return (
  			self.during(year, month)
  			.filter(paid=True)
  			.aggregate(
  				total_amount=models.Sum("amount"), total_refunded=models.Sum("amount_refunded")
  			)
  		)
docs: Return paid Charges during a certain year, month with total amount, fee and refunded annotated.