code: @Nullable
    public DATATYPE getIfChanged (@Nullable final DATATYPE aUnchangedValue)
    {
      return m_eChange.isChanged () ? m_aObj : aUnchangedValue;
    }
docs: Get the store value if this is a change. Otherwise the passed unchanged
  value is returned.
  
  @param aUnchangedValue
  The unchanged value to be used. May be <code>null</code>.
  @return Either the stored value or the unchanged value. May be
  <code>null</code>.