def __delitem__(self, label):
        # Pop the value off, which is akin to deleting it (removes it from the
        # underlying dict). However, we keep it around so we can check if
        # removing it causes an unlabelled point
        value_to_delete = self._labels_to_masks.pop(label)

        try:
            self._verify_all_labels_masked()
        except ValueError as e:
            # Catch the error, restore the value and re-raise the exception!
            self._labels_to_masks[label] = value_to_delete
            raise e
Delete the semantic labelling for the provided label.
dataset/ETHPy150Open menpo/menpo/menpo/landmark/base.py/LandmarkGroup.__delitem__