old_contents: import functools
  
  def wrap_cors(
      func=None,
      *,
      allow_origin='*',
      allow_headers=set(["Origin", "X-Requested-With", "Content-Type", "Accept"])):
      """
      A middleware that allow CORS calls, by adding the
      headers Access-Control-Allow-Origin and Access-Control-Allow-Headers.
      This middlware accepts two optional parameters `allow_origin` and
      `allow_headers` for customization of the headers values. By default
      will be `*` and a set of `[Origin, X-Requested-With, Content-Type, Accept]`
      respectively.
      """
  
      @functools.wraps(func)
      def wrapper(request, *args, **kwargs):
          response = func(request, *args, **kwargs)
  
          if not response.headers:
              response.headers = {}
  
          response.headers['Access-Control-Allow-Origin'] = allow_origin
          response.headers['Access-Control-Allow-Headers'] = ', '.join(allow_headers)
          return response
  
      return wrapper
  
new_contents: import functools
  
  DEFAULT_HEADERS = frozenset(["origin", "x-requested-with", "content-type", "accept"])):
  
  def wrap_cors(func=None, *, allow_origin='*', allow_headers=DEFAULT_HEADERS):
      """
      A middleware that allow CORS calls, by adding the
      headers Access-Control-Allow-Origin and Access-Control-Allow-Headers.
      This middlware accepts two optional parameters `allow_origin` and
      `allow_headers` for customization of the headers values. By default
      will be `*` and a set of `[Origin, X-Requested-With, Content-Type, Accept]`
      respectively.
      """
  
      @functools.wraps(func)
      def wrapper(request, *args, **kwargs):
          response = func(request, *args, **kwargs)
  
          if not response.headers:
              response.headers = {}
  
          response.headers['Access-Control-Allow-Origin'] = allow_origin
          response.headers['Access-Control-Allow-Headers'] = ', '.join(allow_headers)
          return response
  
      return wrapper
  
subject: Put default headers as constant and make it immutable.