def get_bad_smiles(dset, good_idx):
    """
    Get the SMILES whose indices are not in `good_idx`.
    Args:
        dset (nff.data.dataset): NFF dataset
        good_idx (list[int]): indices that you want to keep
    Returns:
        bad_smiles (list[str]): smiles whose indices are not in 
            `good_idx`.
    """
    bad_smiles = [smiles for i, smiles in enumerate(dset.props["smiles"])
                  if i not in good_idx]
    return bad_smiles