def __setitem__(self, label, indices):
        mask = np.zeros(self._pointcloud.n_points, dtype=np.bool)
        mask[indices] = True
        self._labels_to_masks[label] = mask
Add a new label to the landmark group by adding a new set of indices
dataset/ETHPy150Open menpo/menpo/menpo/landmark/base.py/LandmarkGroup.__setitem__