Addeed function return type annotation, try-except block for rdkit import

from deepchem.feat.base_classes import MolecularFeaturizer

from deepchem.utils.molecule_feature_utils import one_hot_encode

from deepchem.utils.typing import RDKitMol, RDKitAtom

import numpy as np

from rdkit import Chem

#from rdkit import Chem

class MATFeaturizer(MolecularFeaturizer):

  >>> import deepchem as dc

  >>> feat = dc.feat.MATFeaturizer()

  >>> out = feat.featurize("CCC")

  Note

  ----

  This class requires RDKit to be installed.

  """

  def __init__(

    self.one_hot_formal_charge = one_hot_formal_charge

  def atom_features(self, atom):

  def atom_features(self, atom : RDKitAtom) -> np.ndarray:

    """

    Deepchem already contains an atom_features function, however we are defining a new one here due to the need to handle features specific to MAT.

    Since we need new features like Atom GetNeighbors and IsInRing, and the number of features required for MAT is a fraction of what the Deepchem atom_features function computes, we can speed up computation by defining a custom function.

    return np.array(attrib, dtype=np.float32)

  def _featurize(self, mol):

  def _featurize(self, mol : RDKitMol) -> np.ndarray:

    """

    Featurize the molecule.

    Tuple[np.ndarray]: (node_features, adjacency_matrix, distance_matrix)

    """

    try:

      from rdkit import Chem

    except:

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

    node_features = np.array(

        [self.atom_features(atom) for atom in mol.GetAtoms()])

    adjacency_matrix = Chem.rdmolops.GetAdjacencyMatrix(mol)