code: def headers_received(self, start_line, headers):
      self.connection.context._apply_xheaders(headers)
      return self.delegate.headers_received(start_line, headers)
  
imports: from __future__ import absolute_import, division, print_function
  import socket
  from tornado.escape import native_str
  from tornado.http1connection import HTTP1ServerConnection, HTTP1ConnectionParameters
  from tornado import gen
  from tornado import httputil
  from tornado import iostream
  from tornado import netutil
  from tornado.tcpserver import TCPServer
  from tornado.util import Configurable
label_desc: Use image node_id 2 for calling the _ProxyAdapter obj's underlying member method code with example usage: obj.headers_received(start_line, headers) and returns: self