libopc/test_docs/subsume_1.xml

<OldElement xmlns:v1="http://schemas.openxmlformats.org/Circles/v1" 
            xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
            xmlns:v2="http://schemas.openxmlformats.org/Circles/v2" 
            mc:Ignorable="v2"
            v2:NewAttribue="value"/>