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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 dict_value_hint(key, mapper=None):
 """Returns a function that takes a dictionary and returns value of particular key. The returned value can be optionally processed by `mapper` function. To be used as a type hint in :class:`OneOf`. """

    if mapper is None:
        mapper = identity

    def hinter(data):
        return mapper(data.get(key))

    return hinter