def find_features_without_taxa(self) -> np.ndarray:
    'Find features without taxa.\n\n        Returns\n        -------\n            class:`~numpy.ndarray` with feature indices.\n        '
    return self.__internal_taxonomy.loc[(self.__internal_taxonomy.loc[:, VALID_RANKS].agg((lambda rank: len(''.join(map((lambda x: str((x or ''))), rank)))), axis=1) < 1)].index.values
Find features without taxa.

Returns
-------
    class:`~numpy.ndarray` with feature indices.
def find_features_without_taxa(self) -> np.ndarray:
    'Find features without taxa.\n\n        Returns\n        -------\n            class:`~numpy.ndarray` with feature indices.\n        '
    return self.__internal_taxonomy.loc[(self.__internal_taxonomy.loc[:, VALID_RANKS].agg((lambda rank: len(.join(map((lambda x: str((x or ))), rank)))), axis=1) < 1)].index.values