<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def isotime(s):
    "Convert timestamps in ISO8661 format to and from Unix time."
    if type(s) == type(1):
        return time.strftime("%Y-%m-%dT%H:%M:%S", time.gmtime(s))
    elif type(s) == type(1.0):
        date = int(s)
        msec = s - date
        date = time.strftime("%Y-%m-%dT%H:%M:%S", time.gmtime(s))
        return date + "." + repr(msec)[3:]
    elif type(s) == type("") or type(s) == type(u""):
        if s[-1] == "Z":
            s = s[:-1]
        if "." in s:
            (date, msec) = s.split(".")
        else:
            date = s
            msec = "0"
        # Note: no leap-second correction! 
        return calendar.timegm(time.strptime(date, "%Y-%m-%dT%H:%M:%S")) + float("0." + msec)
    else:
        raise TypeError