docs: function (request, callback) {
              this.nbXdrRequests += 1;
  
              this.xdrRequests[request.id] = {
                  callback : callback,
                  transaction : request.id
              };
  
              var args = {
                  xdr : true,
                  method : request.method,
                  data : request.data,
                  headers : request.headers
              };
  
              // This might throw an error, propagate it and let the IO know that there was an exception
              this._transport.send(request.url, args, request.id);
          }