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