class_docstr: MACCS Keys Fingerprint.
  
  The MACCS (Molecular ACCess System) keys are one of the most commonly used structural keys.
  Please confirm the details in [1]_, [2]_.
  
  Examples
  --------
  >>> import deepchem as dc
  >>> smiles = 'CC(=O)OC1=CC=CC=C1C(=O)O'
  >>> featurizer = dc.feat.MACCSKeysFingerprint()
  >>> features = featurizer.featurize([smiles])
  >>> type(features[0])
  <class 'numpy.ndarray'>
  >>> features[0].shape
  (167,)
  
  References
  ----------
  .. [1] Durant, Joseph L., et al. "Reoptimization of MDL keys for use in drug discovery."
           Journal of chemical information and computer sciences 42.6 (2002): 1273-1280.
  .. [2] https://github.com/rdkit/rdkit/blob/master/rdkit/Chem/MACCSkeys.py
  
  Note
  ----
  This class requires RDKit to be installed.
docstr: Initialize this featurizer.
docstr_tok: ["Initialize","this","featurizer","."]
code: def __init__(self):
      """Initialize this featurizer."""
      self.calculator = None
  
imports: import numpy
  from deepchem.utils.typing import RDKitMol
  from deepchem.feat.base_classes import MolecularFeaturizer
label_desc: Use image node_id 1 to create a new MACCSKeysFingerprint object from inherited base classes: MolecularFeaturizer with example: obj = MACCSKeysFingerprint()