How to use the nbgitpuller.pull.GitPuller function in nbgitpuller

# The default working directory is the directory from which Jupyter
            # server is launched, which is not the same as the root notebook
            # directory assuming either --notebook-dir= is used from the
            # command line or c.NotebookApp.notebook_dir is set in the jupyter
            # configuration. This line assures that all repos are cloned
            # relative to server_root_dir, so that all repos are always in
            # scope after cloning. Sometimes server_root_dir will include
            # things like `~` and so the path must be expanded.
            repo_dir = os.path.join(os.path.expanduser(self.settings['server_root_dir']),
                                    repo.split('/')[-1])

            # We gonna send out event streams!
            self.set_header('content-type', 'text/event-stream')
            self.set_header('cache-control', 'no-cache')

            gp = GitPuller(repo, branch, repo_dir, depth=depth, parent=self.settings['nbapp'])

            q = Queue()
            def pull():
                try:
                    for line in gp.pull():
                        q.put_nowait(line)
                    # Sentinel when we're done
                    q.put_nowait(None)
                except Exception as e:
                    q.put_nowait(e)
                    raise e
            self.gp_thread = threading.Thread(target=pull)

            self.gp_thread.start()

            while True:

def __init__(self, git_url, branch_name, repo_dir, **kwargs):
        assert git_url and branch_name

        self.git_url = git_url
        self.branch_name = branch_name
        self.repo_dir = repo_dir
        newargs = {k: v for k, v in kwargs.items() if v is not None}
        super(GitPuller, self).__init__(**newargs)