code: def graph(ctx, items, seconds, ylim):
      
      wva = get_wva(ctx)
      es = wva.get_event_stream()
  
      try:
          from wva import grapher
      except ImportError:
          print("Unable to graph... you must have matplotlib installed")
      else:
          stream_grapher = grapher.WVAStreamGrapher(wva, items, seconds=seconds, ylim=ylim)
          es.enable()
          stream_grapher.run()
docs: Present a live graph of the incoming streaming data
  
  This command requires that matplotlib be installed and accessible
  to the application in order to work.  The application reads
  data from the WVA event stream and plots all data for specified
  parameters within some time window.  Subscriptions must be
  set up prior to running this command for it to work.
  
  As an example, let's say that I want to show the last 3 minutes (180 seconds)
  of speed and rpm data for my device.  In that case, I work set up my
  subscriptions and execute the following...
  
  \b
      $ wva subscriptions graph --seconds=180 VehicleSpeed EngineSpeed