text: 
  
  from ...core.context import context
  from ...core.adapter import rank
  from ...core.wsgi import WSGI
  
  
  class CORSWSGI(WSGI):
  
      rank(1.0)
  
      def __call__(self):
          origin = context.app.tweak.cors.origin
          if origin is None:
              return super(CORSWSGI, self).__call__()
          # FIXME: have to replace `self.start_response`.
          old_start_response = self.start_response
          def cors_start_response(status, headers, exc_info=None):
              headers = headers + [('Access-Control-Allow-Origin', origin)]
              return old_start_response(status, headers, exc_info)
          self.start_response = cors_start_response
          return super(CORSWSGI, self).__call__()
  
  
  