code: def unmarshal(self, v):
          
          if not isinstance(v, tzinfo):
              # (GMT-08:00) America/Los_Angeles
              tzname = v.split(' ', 1)[1]
              v = pytz.timezone(tzname)
          return v
docs: Convert a timestamp in format "(GMT-08:00) America/Los_Angeles" to
          a `pytz.timestamp` object.