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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def parse_cache_control_header(value, on_update=None, cls=None):
 """Parse a cache control header. The RFC differs between response and request cache control, this method does not. It's your responsibility to not use the wrong control statements. .. versionadded:: 0.5 The `cls` was added. If not specified an immutable :class:`~werkzeug.datastructures.RequestCacheControl` is returned. :param value: a cache control header to be parsed. :param on_update: an optional callable that is called every time a value on the :class:`~werkzeug.datastructures.CacheControl` object is changed. :param cls: the class for the returned object. By default :class:`~werkzeug.datastructures.RequestCacheControl` is used. :return: a `cls` object. """

    if cls is None:
        cls = RequestCacheControl
    if not value:
        return cls(None, on_update)
    return cls(parse_dict_header(value), on_update)