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`

def purgeDatastream(self, pid, dsID, startDT=None, endDT=None, logMessage=None,
            force=False):
        """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`
        """
        # /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)