def listdir(self, pattern=None):
        """ D.listdir() -> List of items in this directory.

        Use D.files() or D.dirs() instead if you want a listing
        of just files or just subdirectories.

        The elements of the list are path objects.

        With the optional 'pattern' argument, this only lists
        items whose names match the given pattern.
        """
        names = os.listdir(self)
        if pattern is not None:
            names = fnmatch.filter(names, pattern)
        return [self / child for child in names]