code: protected void check(Instances data) throws Exception {
      if (m_Owner == null)
        throw new IllegalStateException("No owner set!");
      if (data == null)
        throw new IllegalStateException("No data provided!");
    }
docs: Hook method for performing checks.
  <br>
  Default implementation only ensures that owner and data are present.
  
  @param data	the data to use
  @throws Exception	if check fails