code: public static ServerRequestQueue getInstance(Context c) {
          if (SharedInstance == null) {
              synchronized (ServerRequestQueue.class) {
                  if (SharedInstance == null) {
                      SharedInstance = new ServerRequestQueue(c);
                  }
              }
          }
          return SharedInstance;
      }
docs: <p>Singleton method to return the pre-initialised, or newly initialise and return, a singleton
  object of the type {@link ServerRequestQueue}.</p>
  
  @param c A {@link Context} from which this call was made.
  @return An initialised {@link ServerRequestQueue} object, either fetched from a
  pre-initialised instance within the singleton class, or a newly instantiated
  object where one was not already requested during the current app lifecycle.