docs: def get_additional_charge_by_identifier(self, recurring_billing_id):
          """
          Query extra charge information of an invoice from its identifier.
  
          Args:
              recurring_billing_id: Identifier of the additional charge.
  
          Returns:
  
          """
          fmt = 'recurringBillItems/{}'.format(recurring_billing_id)
          return self.client._get(self.url + fmt, headers=self.get_headers())