def remove_tracker(fei_sid_or_id, wfid=nil)

      tracker_id =
        if fei_sid_or_id.is_a?(String)
          fei_sid_or_id
        else
          Ruote.to_storage_id(fei_sid_or_id)
        end

      remove([ tracker_id ], wfid)
    end
def remove_tracker(fei_sid_or_id, wfid=nil)

      tracker_id =
        if fei_sid_or_id.is_a?(String)
          fei_sid_or_id
        else
          Ruote.to_storage_id(fei_sid_or_id)
        end

      remove([ tracker_id ], wfid)
    end
Removes a tracker (usually when a 'listen' expression replies to its
 parent expression or is cancelled).