code: public void setAnimationBackend(@Nullable T animationBackend) {
      mAnimationBackend = animationBackend;
      if (mAnimationBackend != null) {
        applyBackendProperties(mAnimationBackend);
      }
    }
docs: Set the animation backend to forward calls to.
  If called with null, the current backend will be removed.
  
  @param animationBackend the backend to use or null to remove the current backend