code: protected <T> T loadByExample (
          final Table<T> table, final T example, final FieldMask mask)
          throws PersistenceException
      {
          return execute(new Operation<T>() {
              public T invoke (Connection conn, DatabaseLiaison liaison)
                  throws SQLException, PersistenceException
              {
                  return table.queryByExample(conn, example, mask).get();
              }
          });
      }
docs: Loads a single object from the specified table that matches the
  supplied example. <em>Note:</em> the query should match one or zero
  records, not more.