def __getitem__(self, group=None):
        if group is None:
            if self.n_groups == 1:
                group = self.group_labels[0]
            else:
                raise ValueError("Cannot use None as a key as there are {} "
                                 "landmark groups".format(self.n_groups))
        return self._landmark_groups[group]
Returns the group for the provided label.
dataset/ETHPy150Open menpo/menpo/menpo/landmark/base.py/LandmarkManager.__getitem__