def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def update_snapshot_status(self, snapshot_id, status, progress):
        """Update the specified snapshot's status."""
        post_body = {
            'status': status,
            'progress': progress
        }
        post_body = json.dumps({'os-update_snapshot_status': post_body})
        url = 'snapshots/%s/action' % str(snapshot_id)
        resp, body = self.post(url, post_body)
        return resp, body