code: def _check_boundaries(self, fragment):
          
          if not isinstance(fragment, SyncMapFragment):
              raise TypeError(u"fragment is not an instance of SyncMapFragment")
          interval = fragment.interval
          if not isinstance(interval, TimeInterval):
              raise TypeError(u"interval is not an instance of TimeInterval")
          if (self.begin is not None) and (interval.begin < self.begin):
              raise ValueError(u"interval.begin is before self.begin")
          if (self.end is not None) and (interval.end > self.end):
              raise ValueError(u"interval.end is after self.end")
docs: Check that the interval of the given fragment
          is within the boundaries of the list.
          Raises an error if not OK.