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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 fetch(self):
 """ Fetch a BalanceInstance :returns: Fetched BalanceInstance :rtype: twilio.rest.api.v2010.account.balance.BalanceInstance """

        params = values.of({})

        payload = self._version.fetch(
            'GET',
            self._uri,
            params=params,
        )

        return BalanceInstance(self._version, payload, account_sid=self._solution['account_sid'], )