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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_refund_transaction(self):
 """Retrieve the refund transaction for this transaction, immediately after refunding. After calling `refund()` to refund a transaction, call this method to retrieve the new transaction representing the refund. """

        try:
            url = self._refund_transaction_url
        except AttributeError:
            raise ValueError("No refund transaction is available for this transaction")

        resp, elem = self.element_for_url(url)
        value = self.value_for_element(elem)
        return value