def add_file(self, filename, overwrite=False):
        """Open given file and add its data by guessing its format. The format
        must be Motorola S-Records, Intel HEX or TI-TXT. Set `overwrite` to
        ``True`` to allow already added data to be overwritten.

        """

        with open(filename, 'r') as fin:
            self.add(fin.read(), overwrite)