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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 set_default_account_by_address(self, b58_address: str):
 """ This interface is used to set default account by given base58 encode address. :param b58_address: a base58 encode address. """

        flag = True
        index = -1
        for acct in self.accounts:
            index += 1
            if acct.b58_address == b58_address:
                flag = False
                break
        if flag:
            raise SDKException(ErrorCode.get_account_by_address_err)
        for i in range(len(self.accounts)):
            self.accounts[i].is_default = False
        self.accounts[index].is_default = True
        self.default_account_address = b58_address