Print the current (unexported) contents of the archive

def contents(self, maxlen=70):
        "Print the current (unexported) contents of the archive"
        lines = []
        if len(self._files) == 0:
            print("Empty %s" % self.__class__.__name__)
            return

        fnames = [self._truncate_name(maxlen=maxlen, *k) for k in self._files]
        max_len = max([len(f) for f in fnames])
        for name,v in zip(fnames, self._files.values()):
            mime_type = v[1].get('mime_type', 'no mime type')
            lines.append('%s : %s' % (name.ljust(max_len), mime_type))
        print('\n'.join(lines))