def engine_activity(engine_id)
      xml = make_xml('EngineActivityRequest', { 'engine-id' => engine_id })
      r   = execute(xml)
      arr = []
      if r.success
        r.res.elements.each('//ScanSummary') do |scan_event|
          arr << ScanSummary.parse(scan_event)
        end
      end
      arr
    end
def engine_activity(engine_id)
      xml = make_xml('EngineActivityRequest', { 'engine-id' => engine_id })
      r   = execute(xml)
      arr = []
      if r.success
        r.res.elements.each('//ScanSummary') do |scan_event|
          arr << ScanSummary.parse(scan_event)
        end
      end
      arr
    end
Provide a list of current scan activities for a specific Scan Engine.

 @return [Array[ScanSummary]] Array of ScanSummary objects associated with
   each active scan on the engine.