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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 fulfill(self, agreement_id, message, account_address, signature, from_account):
 """ Fulfill the sign conditon. :param agreement_id: id of the agreement, hex str :param message: :param account_address: ethereum account address, hex str :param signature: signed agreement hash, hex str :param from_account: Account doing the transaction :return: """

        return self._fulfill(
            agreement_id,
            message,
            account_address,
            signature,
            transact={'from': from_account.address,
                      'passphrase': from_account.password}
        )