code: public SyntheticStorableReferenceAccess<S> getReferenceAccess() {
          if (mReferenceAccess == null) {
              Class<? extends Storable> referenceClass = mBuilder.getStorableClass();
              mReferenceAccess = new SyntheticStorableReferenceAccess<S>
                  (mMasterStorableClass, referenceClass, this);
          }
          return mReferenceAccess;
      }
docs: Build and return access to the generated storable reference class.
  
  @since 1.2.1