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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 wkt_rewind(x, digits = None):
    '''
    reverse WKT winding order

    :param x: [str] WKT string
    :param digits: [int] number of digits after decimal to use for the return string. 
        by default, we use the mean number of digits in your string.

    :return: a string

    Usage::
        
        from pygbif import wkt_rewind
        x = 'POLYGON((144.6 13.2, 144.6 13.6, 144.9 13.6, 144.9 13.2, 144.6 13.2))'
        wkt_rewind(x)
        wkt_rewind(x, digits = 0)
        wkt_rewind(x, digits = 3)
        wkt_rewind(x, digits = 7)
    '''
    z = wkt.loads(x)
    if digits is None:
      coords = z['coordinates']
      nums = __flatten(coords)
      dec_n = [ decimal.Decimal(str(w)).as_tuple().exponent for w in nums ]
      digits = abs(statistics.mean(dec_n))
    else:
      if not isinstance(digits, int):
        raise TypeError("'digits' must be an int")
    wound = rewind(z)
    back_to_wkt = wkt.dumps(wound, decimals = digits)
    return back_to_wkt