code: function (activityId, cfg) {
              this.log("retrieveActivity");
              var requestCfg = {},
                  requestResult,
                  callbackWrapper,
                  requestHeaders;
  
              requestHeaders = cfg.requestHeaders || {};
  
              requestCfg = {
                  url: "activities",
                  method: "GET",
                  params: {
                      activityId: activityId
                  },
                  ignore404: true,
                  headers: requestHeaders
              };
  
              if (typeof cfg.callback !== "undefined") {
                  callbackWrapper = function (err, xhr) {
                      var result = xhr;
  
                      if (err === null) {
                          //
                          // a 404 really shouldn't happen because the LRS can dynamically
                          // build the response based on what has been passed to it, but
                          // don't have the client fail in the condition that it does, because
                          // we can do the same thing
                          //
                          if (xhr.status === 404) {
                              result = new TinCan.Activity(
                                  {
                                      id: activityId
                                  }
                              );
                          }
                          else {
                              result = TinCan.Activity.fromJSON(xhr.responseText);
                          }
                      }
  
                      cfg.callback(err, result);
                  };
                  requestCfg.callback = callbackWrapper;
              }
  
              requestResult = this.sendRequest(requestCfg);
              if (! callbackWrapper) {
                  requestResult.activity = null;
                  if (requestResult.err === null) {
                      if (requestResult.xhr.status === 404) {
                          requestResult.activity = new TinCan.Activity(
                              {
                                  id: activityId
                              }
                          );
                      }
                      else {
                          requestResult.activity = TinCan.Activity.fromJSON(requestResult.xhr.responseText);
                      }
                  }
              }
  
              return requestResult;
          }
docs: Retrieve an activity, when used from a browser sends to the endpoint using the RESTful interface.
  
  @method retrieveActivity
  @param {String} activityId id of the Activity to retrieve
  @param {Object} cfg Configuration options
  @param {Function} [cfg.callback] Callback to execute on completion
  @param {Object} [cfg.requestHeaders] Optional object containing additional headers to add to request
  @return {Object} Value retrieved