'Returns true if the files belonging to this task have already
been imported in a previous session.'

def already_imported(self, toppath, paths):

    if (self.is_resuming(toppath) and all([progress_element(toppath, p) for p in paths])):
        return True
    if (self.config['incremental'] and (tuple(paths) in self.history_dirs)):
        return True
    return False
