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 get_snapshot(self, snapshot_id):
        """Returns the details of a single snapshot."""
        url = "snapshots/%s" % str(snapshot_id)
        resp, body = self.get(url)
        body = json.loads(body)
        return resp, body['snapshot']