docs: def create_additional_charge(self, *, subscription_id, description, plan_value, plan_tax, plan_tax_return_base,
                                   currency):
          """
          Adds extra charges to the respective invoice for the current period.
  
          Args:
              subscription_id: Identification of the subscription
              description:
              plan_value:
              plan_tax:
              plan_tax_return_base:
              currency:
  
          Returns:
  
          """
          payload = {
              "description": description,
              "additionalValues": [
                  {
                      "name": "ITEM_VALUE",
                      "value": plan_value,
                      "currency": currency
                  },
                  {
                      "name": "ITEM_TAX",
                      "value": plan_tax,
                      "currency": currency
                  },
                  {
                      "name": "ITEM_TAX_RETURN_BASE",
                      "value": plan_tax_return_base,
                      "currency": currency
                  }
              ]
          }
          fmt = 'subscriptions/{}/recurringBillItems'.format(subscription_id)
          return self.client._post(self.url + fmt, json=payload, headers=self.get_headers())