def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def toggle_comment(self):
        "Toggle the selected comment tree between visible and hidden"

        current_index = self.nav.absolute_index
        self.content.toggle(current_index)

        # This logic handles a display edge case after a comment toggle. We
        # want to make sure that when we re-draw the page, the cursor stays at
        # its current absolute position on the screen. In order to do this,
        # apply a fixed offset if, while inverted, we either try to hide the
        # bottom comment or toggle any of the middle comments.
        if self.nav.inverted:
            data = self.content.get(current_index)
            if data['hidden'] or self.nav.cursor_index != 0:
                window = self._subwindows[-1][0]
                n_rows, _ = window.getmaxyx()
                self.nav.flip(len(self._subwindows) - 1)
                self.nav.top_item_height = n_rows