✨ add custom repr functions

    """

    raise NotImplementedError('Featurizer is not defined.')

  def __repr__(self) -> str:

    """Convert self to repr representation.

    Returns

    -------

    str

      The string represents the class.

    Examples

    --------

    >>> import deepchem as dc

    >>> dc.feat.CircularFingerprint(size=1024, radius=4)

    CircularFingerprint[radius=4, size=1024, chiral=False, bonds=True, features=False, sparse=False, smiles=False]

    >>> dc.feat.CGCNNFeaturizer()

    CGCNNFeaturizer[radius=8.0, max_neighbors=8, step=0.2]

    """

    args_spec = inspect.getfullargspec(self.__init__)  # type: ignore

    args_names = [arg for arg in args_spec.args if arg != 'self']

    args_info = ''

    for arg_name in args_names:

      args_info += arg_name + '=' + str(self.__dict__[arg_name]) + ', '

    return self.__class__.__name__ + '[' + args_info[:-2] + ']'

  def __str__(self) -> str:

    """Convert class to string.

    """Convert self to str representation.

    Returns

    -------

    >>> import deepchem as dc

    >>> str(dc.feat.CircularFingerprint(size=1024, radius=4))

    'CircularFingerprint_radius_4_size_1024'

    >>> str(dc.feat.CGCNNFeaturizer())

    'CGCNNFeaturizer'

    """

    args_spec = inspect.getfullargspec(self.__init__)  # type: ignore

    args_names = [arg for arg in args_spec.args if arg != 'self']

    args_default_values = list(args_spec.defaults) \

      if args_spec.defaults is not None else []

    # the case some arguments don't have the default value

    args_num = len(args_names)

    args_default_num = len(args_default_values)

    if args_num > args_default_num:

      diff = args_num - args_default_num

      args_default_values = [None] * diff + args_default_values

    assert len(args_names) == len(args_default_values)

    args_default_values = [None for _ in range(args_num)]

    if args_spec.defaults is not None:

      defaults = list(args_spec.defaults)

      args_default_values[-len(defaults):] = defaults

    override_args_info = ''

    for arg_name, default in zip(args_names, args_default_values):