def flush_all(self) -> str:
        """
        
        :return:
        """

        # self.bytes_buffer.seek(0)
        # contents = self.bytes_buffer.read()
        # self.bytes_buffer.truncate(0)
        # self.bytes_buffer.seek(0)

        # if contents is None:
        #     return ''

        contents = self.bytes_buffer.getvalue()
        self.bytes_buffer.truncate(0)
        self.bytes_buffer.seek(0)

        return (
            ''
            if not contents else
            contents.decode(self.source_encoding)
        )