code: def options(self, *args, **kwargs):
          '''
          Return CORS headers for preflight requests
          '''
          # Allow X-Auth-Token in requests
          request_headers = self.request.headers.get('Access-Control-Request-Headers')
          allowed_headers = request_headers.split(',')
  
          # Filter allowed header here if needed.
  
          # Allow request headers
          self.set_header('Access-Control-Allow-Headers', ','.join(allowed_headers))
  
          # Allow X-Auth-Token in responses
          self.set_header('Access-Control-Expose-Headers', 'X-Auth-Token')
  
          # Allow all methods
          self.set_header('Access-Control-Allow-Methods', 'OPTIONS, GET, POST')
  
          self.set_status(204)
          self.finish(f options(self, *args, **kwargs):
          '''
          Return CORS headers for preflight requests
          '''
          # Allow X-Auth-Token in requests
          request_headers = self.request.headers.get('Access-Control-Request-Headers')
          allowed_headers = request_headers.split(',')
  
          # Filter allowed header here if needed.
  
          # Allow request headers
          self.set_header('Access-Control-Allow-Headers', ','.join(allowed_headers))
  
          # Allow X-Auth-Token in responses
          self.set_header('Access-Control-Expose-Headers', 'X-Auth-Token')
  
          # Allow all methods
          self.set_header('Access-Control-Allow-Methods', 'OPTIONS, GET, POST')
  
          self.set_status(204)
          self.finish()
docs: Return CORS headers for preflight requests