old_contents: from emit import Router
  from emit.multilang import ShellNode
  
  router = Router()
  
  @router.node(['n'])
  class PythonShellNode(ShellNode):
      command = 'python test.py'
  
  @router.node(['n'])
  class RubyShellNode(ShellNode):
      command = 'bundle exec ruby test.rb'
  
new_contents: from emit import Router
  from emit.multilang import ShellNode
  
  router = Router()
  
  @router.node(('n',))
  class PythonShellNode(ShellNode):
      command = 'python test.py'
  
  @router.node(('n',))
  class RubyShellNode(ShellNode):
      command = 'bundle exec ruby test.rb'
  
subject: change list to tuples in multilang example