<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def created_on(self):
 """The created timestamp of the bucket as a datetime.datetime."""

    s = self._info.get('timeCreated', None)
    return dateutil.parser.parse(s) if s else None