docs: function mixinProxying(agent, proxyOpts) {
    agent.proxy = proxyOpts;
  
    var orig = _.pick(agent, 'createConnection', 'addRequest');
  
    // Make the tcp or tls connection go to the proxy, ignoring the
    // destination host:port arguments.
    agent.createConnection = function(port, host, options) {
      return orig.createConnection.call(this,
                                        this.proxy.port, this.proxy.host, options);
    };
  
    // tell the proxy where we really want to go by fully-qualifying the path
    // part. Force a localAddress if one was configured
    agent.addRequest = function(req, host, port, localAddress) {
      req.path = this.proxy.innerProtocol + '//' + host + ':' + port + req.path;
      if (this.proxy.localAddress) {
        localAddress = this.proxy.localAddress;
      }
      return orig.addRequest.call(this, req, host, port, localAddress);
    };
  }