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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 paypal_time(time_obj=None):
 """Returns a time suitable for PayPal time fields."""

    warn_untested()
    if time_obj is None:
        time_obj = time.gmtime()
    return time.strftime(PayPalNVP.TIMESTAMP_FORMAT, time_obj)