code: @Override
      public Object beforeDelete(S storable) throws PersistException {
          S existing = (S) storable.copy();
          try {
              if (!existing.tryLoad()) {
                  existing = null;
              }
              return existing;
          } catch (FetchException e) {
              throw e.toPersistException();
          }
      }
docs: Returns existing Storable or null