https://github.com/ethereum/go-ethereum/wiki/Management-APIs#personal_sign

        :param message: Message for sign
        :type message: str

        :param account: Account address
        :type account: str

        :param password: Password of account (optional)
        :type password: str

        :return: signature
        :rtype: str

def personal_sign(self, message, account, password=None):
        """https://github.com/ethereum/go-ethereum/wiki/Management-APIs#personal_sign

        :param message: Message for sign
        :type message: str

        :param account: Account address
        :type account: str

        :param password: Password of account (optional)
        :type password: str

        :return: signature
        :rtype: str
        """
        return (yield from self.rpc_call('personal_sign',
                                         [message, account, password]))