code: def append_utc_timestamp(self, tag, timestamp=None, precision=3,
                               header=False):
          
  
          return self._append_utc_datetime(tag,
                                           "%Y%m%d-%H:%M:%S",
                                           timestamp,
                                           precision,
                                           header)
docs: Append a field with a UTCTimestamp value.
  
          :param tag: Integer or string FIX tag number.
          :param timestamp: Time value, see below.
          :param precision: Number of decimal places: 0, 3 (ms) or 6 (us).
          :param header: Append to FIX header if True; default to body.
  
          The `timestamp` value should be a datetime, such as created by
          datetime.datetime.utcnow(); a float, being the number of seconds
          since midnight 1 Jan 1970 UTC, such as returned by time.time();
          or, None, in which case datetime.datetime.utcnow() is used to
          get the current UTC time.
  
          Precision values other than zero (seconds), 3 (milliseconds),
          or 6 (microseconds) will raise an exception.  Note that prior
          to FIX 5.0, only values of 0 or 3 comply with the standard.