def __init__(
        self, transformer: FittableDataTransformer, transform_mask: list[bool]
    ):
        """
        Parameters
        ----------
        transformer
            A `FittableDataTransformer` object with a `fit_transform()` and `transform()` method.
        transform_mask
            A boolean 1-D mask specifying which of the input covariates to :meth:`transform()
            <SequentialEncoderTransformer.transform()>` must be transformed.
        """
        self.transformer: FittableDataTransformer = transformer
        self.transform_mask: np.ndarray = np.array(transform_mask)
        self._fit_called: bool = False

        Parameters
        ----------
        transformer
            A `FittableDataTransformer` object with a `fit_transform()` and `transform()` method.
        transform_mask
            A boolean 1-D mask specifying which of the input covariates to :meth:`transform()
            <SequentialEncoderTransformer.transform()>` must be transformed.
        
darts/dataprocessing/encoders/encoder_base.py