docs: def do_OPTIONS(self):
          """Handles an OPTIONS request."""
          thread_local.clock_start = get_time()
          thread_local.status_code = 200
          thread_local.message = None
          thread_local.headers = []
          thread_local.end_headers = []
          thread_local.size = -1
          thread_local.method = 'OPTIONS'
          self.send_response(200)
          if self.is_cross_origin():
              no_caching = self.cross_origin_headers()
              # ten minutes if no custom headers requested
              self.send_header("Access-Control-Max-Age",
                               0 if no_caching else 10*60)
          self.send_header("Content-Length", 0)
          self.end_headers()
          thread_local.size = 0