<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def iso8601(self):
 """Returns an ISO 8601 representation of the MayaDT."""

        # Get a timezone-naive datetime.
        dt = self.datetime(naive=True)
        return '{}Z'.format(dt.isoformat())