

def parse_set_header(value, on_update=None):
    'Parse a set-like header and return a\n    :class:`~werkzeug.datastructures.HeaderSet` object:\n\n    >>> hs = parse_set_header(\'token, "quoted value"\')\n\n    The return value is an object that treats the items case-insensitively\n    and keeps the order of the items:\n\n    >>> \'TOKEN\' in hs\n    True\n    >>> hs.index(\'quoted value\')\n    1\n    >>> hs\n    HeaderSet([\'token\', \'quoted value\'])\n\n    To create a header from the :class:`HeaderSet` again, use the\n    :func:`dump_header` function.\n\n    :param value: a set header to be parsed.\n    :param on_update: an optional callable that is called every time a\n                      value on the :class:`~werkzeug.datastructures.HeaderSet`\n                      object is changed.\n    :return: a :class:`~werkzeug.datastructures.HeaderSet`\n    '
    if (not value):
        return HeaderSet(None, on_update)
    return HeaderSet(parse_list_header(value), value)

dataset/ETHPy150Open Eforcers/gae-flask-todo/lib/werkzeug/http.py parse_set_header/VarMisuse@41/366 `on_update`->`value`