def METHOD_NAME(self):
    index = self.current_index + 1
    total_files = len(self.properties)
    total_size = human_size(self.total_size)
    if self.total_length:
        self.set_title(_("File Properties (%(num)i of %(total)i  /  %(size)s  /  %(length)s)") % {
            "num": index, "total": total_files, "size": total_size,
            "length": human_length(self.total_length)
        })
        return
    self.set_title(_("File Properties (%(num)i of %(total)i  /  %(size)s)") % {
                   "num": index, "total": total_files, "size": total_size})