code: function(resp, options) {
          var opt = options[resp.requestType];
          if(opt && opt.callback) {
              opt.callback.call(opt.scope, resp);
          }
      }
docs: Method: callUserCallback
  This method is used from within the commit method each time an
  an HTTP response is received from the server, it is responsible
  for calling the user-supplied callbacks.
  
  Parameters:
  resp - {<OpenLayers.Protocol.Response>}
  options - {Object} The map of options passed to the commit call.