def __init__(self, groups=None):
        super(GroupedRequirements, self).__init__(NamedRequirements)
        self.groups = groups or self.default_groups
        self.filename = None
        self.create_default_groups()
def list_snapshots(self, params=None):
        """List all the snapshot."""
        url = 'snapshots'
        if params:
                url += '?%s' % urllib.urlencode(params)

        resp, body = self.get(url)
        body = json.loads(body)
        return resp, body['snapshots']