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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 _getCampaignDict():
 """Returns a dictionary specifying the details of all campaigns."""

    global _campaign_dict_cache
    if _campaign_dict_cache is None:
        # All pointing parameters and dates are stored in a JSON file
        fn = os.path.join(PACKAGEDIR, "data", "k2-campaign-parameters.json")
        _campaign_dict_cache = json.load(open(fn))
    return _campaign_dict_cache