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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 append_diff_hist(diff, diff_hist=list()):
 """Given a diff as generated by record_diff, append a diff record to the list of diff_hist records."""

    diff, diff_hist = _norm_json_params(diff, diff_hist)

    if not diff_hist:
        diff_hist = list()

    diff_hist.append({'diff': diff, 'diff_date': now_field()})
    return diff_hist