How to use the grimoirelab.toolkit.datetime.str_to_datetime function in grimoirelab

closed_at = issue['closed_at']
            if closed_at:
                closed_at = str_to_datetime(issue['closed_at'])

            bug, created = self.object.bugs.get_or_create(
                bug_id=str(issue['number']),
                defaults={'close_date': closed_at,
                          'severity': None})

            logger.info("%s bug [%s]",
                        "Imported" if created else "Found",
                        bug)

            if created:
                bug_create_time = str_to_datetime(issue['created_at'])
                comment = bug.comments.create(comment_id='VIRTUAL-1',
                                              author=self.get_user(
                                                  issue['user_data']),
                                              timestamp=bug_create_time)
                self.record_timestamp(bug_create_time)
                logger.info("Imported bug body as [%s]", comment)

        # TODO: not supported yet
        comments = []

        # Import comments
        for comment in comments:
            issue_number = os.path.basename(comment['issue_url'])
            bug = self.object.bugs.get(bug_id=issue_number)
            extrafields = {
                'author': self.get_user(comment['user']['login']),

def _import_comment(self, bug, comment_id, author, timestamp):
        """
        Import comment into `bug'.

        @arg bug btinfo.models.Bug object to import comment for
        @arg comment_id String representing comment ID
        @arg author Jira user
        @arg timestamp String timestamp in iso8601 form

        @returns True if comment was created, otherwise false
        """
        timestamp = str_to_datetime(timestamp)

        name = author['displayName']
        email = author.get('emailAddress', None)

        author = get_participant(name, email)

        _, created = bug.comments.get_or_create(
            comment_id=comment_id,
            defaults={
                'author': author,
                'timestamp': timestamp})

        if created:
            self.record_timestamp(timestamp)

        return created

if not created:
                bug.severity = severity
                bug.save()
            else:
                logger.info("Saving initial comment for [%s]", bug)
                bug.comments.create(
                    comment_id='VIRTUAL-1',
                    author=self.getuser(data['author_data']),
                    timestamp=str_to_datetime(data['created_on'])
                )

            last_closed_time = None

            for journal in data['journals']:
                journal_time = str_to_datetime(journal['created_on'])
                comment, created = bug.comments.get_or_create(
                    comment_id=journal['id'],
                    author=self.getuser(journal['user_data']),
                    timestamp=journal_time)

                logger.info("%s comment [%s]",
                            "Created" if created else "Found", comment)

                if self.journal_is_closing_entry(journal):
                    last_closed_time = journal_time

            if last_closed_time is not None:
                bug.close_date = last_closed_time
                bug.save()

bug, created = self.object.bugs.get_or_create(bug_id=data['id'],
                                                          defaults={'severity': severity})

            logger.info("%s bug [%s]",
                        "Created" if created else "Found", bug)

            if not created:
                bug.severity = severity
                bug.save()
            else:
                logger.info("Saving initial comment for [%s]", bug)
                bug.comments.create(
                    comment_id='VIRTUAL-1',
                    author=self.getuser(data['author_data']),
                    timestamp=str_to_datetime(data['created_on'])
                )

            last_closed_time = None

            for journal in data['journals']:
                journal_time = str_to_datetime(journal['created_on'])
                comment, created = bug.comments.get_or_create(
                    comment_id=journal['id'],
                    author=self.getuser(journal['user_data']),
                    timestamp=journal_time)

                logger.info("%s comment [%s]",
                            "Created" if created else "Found", comment)

                if self.journal_is_closing_entry(journal):
                    last_closed_time = journal_time

dj_bug.severity = self.translate_severity(bug['bug_severity'][0]['__text__'])
            dj_bug.save()
            if 'long_desc' not in bug:
                bug['long_desc'] = []

            for comment in bug['long_desc']:
                comment_id = comment['commentid'][0]['__text__']
                logger.debug("Comment is: %s", comment_id)

                author = comment['who'][0]
                real_name = author['name']
                email = author['__text__']
                if email.find('@') < 0:
                    email = None
                author = get_participant(real_name, email)
                posting_date = str_to_datetime(comment['bug_when'][0]['__text__'])

                dj_comment, created = dj_bug.comments.get_or_create(
                    comment_id=comment_id,
                    defaults=dict(timestamp=posting_date,
                                  author=author))

                dirty = False
                if dj_comment.timestamp != posting_date:
                    dirty = True
                    dj_comment.timestamp = posting_date
                    logger.warning("Fixing timestamp of [%s]",
                                   dj_comment)
                if dj_comment.author != author:
                    dirty = True
                    logger.warning("Fixing author of [%s], from [%s] to [%s]",
                                   dj_comment, dj_comment.author, author)

# None. Check directly to avoid python-bugzilla's
            # autorefreshing if it doesn't exist.
            if 'cf_last_closed' in bug and bug['cf_last_closed'][0]['__text__']:
                last_closed_date = bug['cf_last_closed'][0]['__text__']


            # FIXME: For now we assume that the last change time is when the
            # bug was closed, but that is not always the case. We should look
            # into calling Bug::history to get this information.
            elif bug['resolution']:
                last_closed_date = bug['delta_ts'][0]['__text__']
            else:
                last_closed_date = None

            if last_closed_date:
                last_closed_date = str_to_datetime(last_closed_date)

            if last_closed_date and last_closed_date != dj_bug.close_date:
                self.record_timestamp(last_closed_date)

            dj_bug.close_date = last_closed_date

            dj_bug.severity = self.translate_severity(bug['bug_severity'][0]['__text__'])
            dj_bug.save()
            if 'long_desc' not in bug:
                bug['long_desc'] = []

            for comment in bug['long_desc']:
                comment_id = comment['commentid'][0]['__text__']
                logger.debug("Comment is: %s", comment_id)

                author = comment['who'][0]

def _run(self):
        for bug in self.iter_bugs():
            issue = bug['data']
            cl_date = issue['fields']['resolutiondate']

            if cl_date:
                close_date = str_to_datetime(cl_date)
            else:
                close_date = None

            try:
                with transaction.atomic():
                    bug, created = self.object.bugs.get_or_create(
                        bug_id=issue['key'],
                        defaults={'close_date': close_date})

                    logger.info("%s bug [%s]",
                                "Imported" if created else "Found",
                                issue['key'])

                    # Create first comment, since that seems to be merged into
                    # the issue
                    if created: