code: function () {
          var auth = E;
  
          // Add authentication method to URL if the same is requested. We do it this way because
          // this is how `postman-request` library accepts auth credentials in its proxy configuration.
          if (this.authenticate) {
              auth = (this.username || E);
  
              if (this.password) {
                  auth += (COLON + (this.password || E));
              }
  
              if (auth) {
                  auth += AUTH_CREDENTIALS_SEPARATOR;
              }
          }
  
          return DEFAULT_PROTOCOL + PROTOCOL_HOST_SEPARATOR + auth + this.host + COLON + this.port;
      }
docs: Returns the proxy server url.
  
  @returns {String}