code: public void setCallback2(@Nullable Callback callback) {
  
          this.callback = callback;
          super.setCallback(callback);
  
          // if not null -> means we are attached
          if (callback != null) {
  
              // as we have a placeholder now, it's important to check it our placeholder
              // has a proper callback at this point. This is not required in most cases,
              // as placeholder should be static, but if it's not -> it can operate as usual
              if (result != null
                      && result.getCallback() == null) {
                  result.setCallback(callback);
              }
  
              loader.load(destination, this);
          } else {
              if (result != null) {
  
                  result.setCallback(null);
  
                  // let's additionally stop if it Animatable
                  if (result instanceof Animatable) {
                      ((Animatable) result).stop();
                  }
              }
              loader.cancel(destination);
          }
      }
docs: yeah