code: def view_graph(graph_str, dest_file=None):
      
      from rez.system import system
      from rez.config import config
  
      if (system.platform == "linux") and (not os.getenv("DISPLAY")):
          print >> sys.stderr, "Unable to open display."
          sys.exit(1)
  
      dest_file = _write_graph(graph_str, dest_file=dest_file)
  
      # view graph
      viewed = False
      prog = config.image_viewer or 'browser'
      print "loading image viewer (%s)..." % prog
  
      if config.image_viewer:
          proc = popen([config.image_viewer, dest_file])
          proc.wait()
          viewed = not bool(proc.returncode)
  
      if not viewed:
          import webbrowser
          webbrowser.open_new("file://" + dest_file)
docs: View a dot graph in an image viewer.