code: def purgeDatastream(self, pid, dsID, startDT=None, endDT=None, logMessage=None,
              force=False):
          
          # /objects/{pid}/datastreams/{dsID} ? [startDT] [endDT] [logMessage] [force]
          http_args = {}
          if logMessage:
              http_args['logMessage'] = logMessage
          if startDT:
              http_args['startDT'] = startDT
          if endDT:
              http_args['endDT'] = endDT
          if force:
              http_args['force'] = force
  
          url = 'objects/%(pid)s/datastreams/%(dsid)s' % {'pid': pid, 'dsid': dsID}
          return self.delete(url, params=http_args)
docs: Purge a datastream, or specific versions of a dastream, from
          a Fedora object.  On success, response content will include
          a list of timestamps for the purged datastream versions; on failure,
          response content may contain an error message.
  
          :param pid: object pid
          :param dsID: datastream ID
          :param startDT: optional start datetime (when purging specific versions)
          :param endDT: optional end datetime (when purging specific versions)
          :param logMessage: optional log message
  
          :rtype: :class:`requests.models.Response`