def convert_timestamp(ts):
return ts.replace(microsecond=<NUM_LIT:0>).isoformat() + '<STR_LIT>'<EOL>
Converts the timestamp to a format suitable for Billing.

    Examples of a good timestamp for startTime, endTime, and eventTime:
        '2016-05-20T00:00:00Z'
    We must drop microseconds so that Yagi does not get upset.
    Note the trailing 'Z'. Python does not add the 'Z' so we tack it on
    ourselves.