remove rdkit mol req

                log_every_n: int = 1000) -> np.ndarray:

    """Calculate features for datapoints.

    `**kwargs` will get passed directly to `Featurizer._featurize`

    Parameters

    ----------

    datapoints: Iterable[Any]

    self.attention_mask = attention_mask

    return

  def _featurize(self, mol: RDKitMol) -> List[List[int]]:

  def _featurize(self, smiles_string: str) -> List[List[int]]:

    """Calculate encoding using HuggingFace's RobertaTokenizerFast

    Parameters

    ----------

        mol: rdkit.Chem.rdchem.Mol

          RDKit Mol object

    smiles_string: str

      String containing SMILES sequence.

    Returns

    -------

    encoding: List

      List containing two lists; the `input_ids` and the `attention_mask`

    """

    try:

      from rdkit import Chem

    except ModuleNotFoundError:

      raise ImportError("This class requires RDKit to be installed.")

    smiles_string = Chem.MolToSmiles(mol)

    # the encoding is natively a dictionary with keys 'input_ids' and 'attention_mask'

    # -> make this a list of two lists to allow np to handle it

    # encoding = list(self(smiles_string, **kwargs).values())