def extract_labels(self) -> np.ndarray:
        """Extract condition labels.

        Returns
        -------
        np.ndarray
            The condition label of each epoch.
        """
        condition_idxs, epoch_idxs, _ = np.where(self)
        _, unique_epoch_idxs = np.unique(epoch_idxs, return_index=True)
        return condition_idxs[unique_epoch_idxs]
Extract condition labels.

        Returns
        -------
        np.ndarray
            The condition label of each epoch.