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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 RegisterKey(cls, key, getter=None, setter=None, deleter=None, lister=None):
 """Register a new key mapping. A key mapping is four functions, a getter, setter, deleter, and lister. The key may be either a string or a glob pattern. The getter, deleted, and lister receive an MP4Tags instance and the requested key name. The setter also receives the desired value, which will be a list of strings. The getter, setter, and deleter are used to implement __getitem__, __setitem__, and __delitem__. The lister is used to implement keys(). It should return a list of keys that are actually in the MP4 instance, provided by its associated getter. """

        key = key.lower()
        if getter is not None:
            cls.Get[key] = getter
        if setter is not None:
            cls.Set[key] = setter
        if deleter is not None:
            cls.Delete[key] = deleter
        if lister is not None:
            cls.List[key] = lister