code: def datastream_lastmodified(request, pid, dsid, repo=None,
      as_of_date=None, *args, **kwargs):
      '''Method suitable for use as a a last-modified function with
      :class:`django.views.decorators.http.condition`.  Takes basically
      the same arguments as :meth:`~eulfedora.views.raw_datastream`.
      '''
      try:
          if repo is None:
              repo = Repository()
          resp = repo.api.getDatastream(pid, dsid, asOfDateTime=as_of_date)
          dsprofile = parse_xml_object(DatastreamProfile, resp.content, resp.url)
          if dsprofile:
              return dsprofile.created
      except RequestFailed:
          pasf datastream_lastmodified(request, pid, dsid, repo=None,
      as_of_date=None, *args, **kwargs):
      '''Method suitable for use as a a last-modified function with
      :class:`django.views.decorators.http.condition`.  Takes basically
      the same arguments as :meth:`~eulfedora.views.raw_datastream`.
      '''
      try:
          if repo is None:
              repo = Repository()
          resp = repo.api.getDatastream(pid, dsid, asOfDateTime=as_of_date)
          dsprofile = parse_xml_object(DatastreamProfile, resp.content, resp.url)
          if dsprofile:
              return dsprofile.created
      except RequestFailed:
          pass
docs: Method suitable for use as a a last-modified function with
      :class:`django.views.decorators.http.condition`.  Takes basically
      the same arguments as :meth:`~eulfedora.views.raw_datastream`.