def METHOD_NAME(nb):
    """
    Create a copy of a notebook with ignored lines stripped.
    Args:
        nb (``nbformat.NotebookNode``): the notebook to strip
    Returns:
        ``nbformat.NotebookNode``: a copy of ``nb`` with ignored line stripped
    """
    nb = copy.deepcopy(nb)
    for cell in nb['cells']:
        cell['source'] = '\n'.join(remove_ignored_lines(get_source(cell)))
    return nb