public static RequestManager with(Activity activity) {
        RequestManagerRetriever retriever = RequestManagerRetriever.get();
        return retriever.get(activity);
    }
Begin a load with Glide that will be tied to the given {@link Activity}'s lifecycle and that uses the
given {@link Activity}'s default options.

@param activity The activity to use.
@return A RequestManager for the given activity that can be used to start a load.
core/src/main/java/com/bumptech/glide/Glide.java