def __init__(
        self,
        input_key: str,
        output_key: Optional[str] = None,
        rootpath: Optional[str] = None,
        grayscale: bool = False,
    ):
        """
        Args:
            input_key: key to use from annotation dict
            output_key: key to use to store the result,
                default: ``input_key``
            rootpath: path to images dataset root directory
                (so your can use relative paths in annotations)
            grayscale: flag if you need to work only
                with grayscale images
        """
        super().__init__(input_key, output_key or input_key)
        self.rootpath = rootpath
        self.grayscale = grayscale

        Args:
            input_key: key to use from annotation dict
            output_key: key to use to store the result,
                default: ``input_key``
            rootpath: path to images dataset root directory
                (so your can use relative paths in annotations)
            grayscale: flag if you need to work only
                with grayscale images
        
catalyst/contrib/data/reader_cv.py