def preprocess(self, payload: str | None) -> str | None:
        """
        Parameters:
            payload: Color as hex string
        Returns:
            Passes selected color value as a hex `str` into the function.
        """
        if payload is None:
            return None
        else:
            return str(payload)

        Parameters:
            payload: Color as hex string
        Returns:
            Passes selected color value as a hex `str` into the function.
        
gradio/components/color_picker.py