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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 _add_commas(s, sep=','):
 """Add commas to output counts. From: http://code.activestate.com/recipes/498181 """

    if len(s) <= 3:
        return s

    return _add_commas(s[:-3], sep) + sep + s[-3:]