How to use the ara.models.db.session.commit function in ara

def test_duplicate_host(self):
        host = m.Host(
            name='localhost',
            playbook=self.playbook,
        )
        m.db.session.add(host)

        with self.assertRaises(Exception):
            m.db.session.commit()

"""
        LOG.debug('logging stats')
        hosts = sorted(stats.processed.keys())
        for hostname in hosts:
            host = self.get_or_create_host(hostname)
            host_stats = stats.summarize(hostname)
            db.session.add(models.Stats(
                playbook=self.playbook,
                host=host,
                changed=host_stats['changed'],
                unreachable=host_stats['unreachable'],
                failed=host_stats['failures'],
                ok=host_stats['ok'],
                skipped=host_stats['skipped']
            ))
            db.session.commit()

def close_play(self):
        """
        Marks the completion time of the currently active play.
        """
        if self.play is not None:
            LOG.debug('closing play %s (%s)', self.play.name, self.play.id)
            self.play.stop()
            db.session.add(self.play)
            db.session.commit()

            self.play = None

def close_playbook(self):
        """
        Marks the completion time of the currently active playbook.
        """
        if self.playbook is not None:
            log.debug('Closing playbook %s', self.playbook.path)
            self.playbook.stop()
            self.playbook.complete = True
            db.session.add(self.playbook)
            db.session.commit()

def get_or_create_file(self, path):
        try:
            if self.playbook.id:
                file_ = (models.File.query
                         .filter_by(path=path)
                         .filter_by(playbook_id=self.playbook.id)
                         .one())
                return file_
        except models.NoResultFound:
            pass

        file_ = models.File(path=path, playbook=self.playbook)
        db.session.add(file_)
        db.session.commit()

        try:
            with open(path, 'r') as fd:
                data = fd.read()
            sha1 = models.content_sha1(data)
            content = models.FileContent.query.get(sha1)

            if content is None:
                content = models.FileContent(content=data)

            file_.content = content
        except IOError:
            LOG.warn('failed to open %s for reading', path)

        return file_

def get_or_create_file(self, path):
        try:
            if self.playbook.id:
                file_ = (models.File.query
                         .filter_by(path=path)
                         .filter_by(playbook_id=self.playbook.id)
                         .one())
                return file_
        except models.NoResultFound:
            pass

        file_ = models.File(path=path, playbook=self.playbook)
        db.session.add(file_)
        db.session.commit()

        try:
            with open(path, 'r') as fd:
                data = fd.read()
            sha1 = models.content_sha1(data)
            content = models.FileContent.query.get(sha1)

            if content is None:
                content = models.FileContent(content=data)

            file_.content = content
        except IOError:
            log.warning('failed to open %s for reading', path)

        return file_

self.close_task()
        self.close_play()

        log.debug('Starting play %s', play.name)
        if self.play is not None:
            self.play.stop()

        self.play = models.Play(
            name=play.name,
            sortkey=next(self.play_counter),
            playbook=self.playbook
        )

        self.play.start()
        db.session.add(self.play)
        db.session.commit()

def get_or_create_host(self, hostname):
        try:
            host = (models.Host.query
                    .filter_by(name=hostname)
                    .filter_by(playbook_id=self.playbook.id)
                    .one())
        except models.NoResultFound:
            host = models.Host(name=hostname, playbook=self.playbook)
            db.session.add(host)
            db.session.commit()

        return host