How to use the changelog.gerrit.GerritThing function in changelog

self.labels = {}
        for lbl in obj['labels']:
            self.labels[lbl] = {}
            for k, v in obj['labels'][lbl].items():
                if k in ('blocking', 'value', 'default_value'):
                    self.labels[lbl][k] = v
                elif k in ('approved', 'rejected', 'recommended', 'disliked'):
                    self.labels[lbl][k] = GerritUser(url, v)
                else:
                    print("Unknown label: %s" % k)

    def __str__(self):
        return 'GerritChange[status={},url={},project={},branch={},change_id={}]'.format(self.status, self._url, self.project,
                self.branch, self.change_id)

class GerritListing(GerritThing):
    """Represents a listing page on Gerrit (e.g. /changes/ or /projects/)"""
    def __init__(self, url, path, params, clazz, limit=-1):
        super(GerritListing, self).__init__(url)
        self.params = params
        self.path = path
        self._item_cache = []
        self._item_index = 0
        self._start = 0
        self._clazz = clazz
        self._limit = limit

    def _load_page(self):
        params = self.params
        params['S'] = self._start
        obj = self._do_request(self.path, params)
        appended = 0

raise StopIteration
        if self._item_index + 1 > len(self._item_cache):
            added = self._load_page()
            self._start += self.params['n']
            if added == 0:
                raise StopIteration
        self._item_index += 1
        return self._item_cache[self._item_index - 1]

    next = __next__

    def __str__(self):
        return 'GerritListing[path={},params={},clazz={},index={},cache_len={}]'.format(self.path, self.params,
                self._clazz, self._item_index, len(self._item_cache))

class GerritServer(GerritThing):
    """Represents a Gerrit server"""
    def __init__(self, url):
        super(GerritServer ,self).__init__(url)

    def changes(self, query='status:merged', n=50, limit=-1):
        # O is a bitmask in hex - see https://github.com/gerrit-review/gerrit/blob/master/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/client/ListChangesOption.java
        params = { 'q': query, 'n': n, 'O': '81' }
        return GerritListing(self._url, '/changes/', params, GerritChange, limit)

self.username = obj.get('username', obj['name'])
        except KeyError:
            self.username = 'unknown'
        try:
            self.name = obj.get('name', obj['username'])
        except KeyError:
            self.name = 'Anonymous Coward'
        try:
            self.email = obj['email']
        except KeyError:
            self.email = 'unknown'
        self.avatars = {}
        for i in obj['avatars']:
            self.avatars[i['height']] = i['url']

class GerritChange(GerritThing):
    """Represents a single change."""
    def __init__(self, url, obj):
        super(GerritChange, self).__init__(url)
        self._id = obj['id']
        self.project = obj['project']
        self.branch = obj['branch']
        self.change_id = obj['change_id']
        self.subject = obj['subject']
        self.status = obj['status']
        self.created = parse_gerrit_datetime(obj['created'])
        self.updated = parse_gerrit_datetime(obj['updated'])
        self.submitted = parse_gerrit_datetime(obj.get('submitted', None))
        self.number = obj['_number']
        self.url = self._url + '/' + str(self.number)
        self.owner = GerritUser(url, obj['owner'])
        self.labels = {}

return d.strftime('"%Y-%m-%d %H:%M:%S"')

class GerritThing(object):
    def __init__(self, url):
        self._url = url

    def _do_request(self, path, params):
        r = requests.get(self._url + path, params=params)
        text = r.text[5:]
        try:
            return json.loads(text)
        except Exception:
            print(text)
            return {}

class GerritUser(GerritThing):
    """Represents a user"""
    def __init__(self, url, obj):
        super(GerritUser, self).__init__(url)
        self.id = obj['_account_id']
        try:
            self.username = obj.get('username', obj['name'])
        except KeyError:
            self.username = 'unknown'
        try:
            self.name = obj.get('name', obj['username'])
        except KeyError:
            self.name = 'Anonymous Coward'
        try:
            self.email = obj['email']
        except KeyError:
            self.email = 'unknown'