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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 checkTimestamp(nonce_string, allowed_skew=SKEW, now=None):
 """Is the timestamp that is part of the specified nonce string within the allowed clock-skew of the current time? @param nonce_string: The nonce that is being checked @type nonce_string: str @param allowed_skew: How many seconds should be allowed for completing the request, allowing for clock skew. @type allowed_skew: int @param now: The current time, as a Unix timestamp @type now: int @returntype: bool @returns: Whether the timestamp is correctly formatted and within the allowed skew of the current time. """

    try:
        stamp, _ = split(nonce_string)
    except ValueError:
        return False
    else:
        if now is None:
            now = time()

        # Time after which we should not use the nonce
        past = now - allowed_skew

        # Time that is too far in the future for us to allow
        future = now + allowed_skew

        # the stamp is not too far in the future and is not too far in
        # the past
        return past <= stamp <= future