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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 split(nonce_string):
 """Extract a timestamp from the given nonce string @param nonce_string: the nonce from which to extract the timestamp @type nonce_string: str @returns: A pair of a Unix timestamp and the salt characters @returntype: (int, str) @raises ValueError: if the nonce does not start with a correctly formatted time string """

    timestamp_str = nonce_string[:time_str_len]
    try:
        timestamp = timegm(strptime(timestamp_str, time_fmt))
    except AssertionError: # Python 2.2
        timestamp = -1
    if timestamp < 0:
        raise ValueError('time out of range')
    return timestamp, nonce_string[time_str_len:]