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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 _get_update_fn(strategy):
 """ Select dict-like class based on merge strategy and orderness of keys. :param merge: Specify strategy from MERGE_STRATEGIES of how to merge dicts. :return: Callable to update objects """

    if strategy is None:
        strategy = MS_DICTS
    try:
        return _MERGE_FNS[strategy]
    except KeyError:
        if callable(strategy):
            return strategy

        raise ValueError("Wrong merge strategy: %r" % strategy)