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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_account_balance(self, account):
 """ What's the balance of an account? Aborts if its negative """

        balance = namedb_get_account_balance(account)
        assert isinstance(balance, (int,long)), 'BUG: account balance of {} is {} (type {})'.format(account['address'], balance, type(balance))
        return balance