void 
GusdGU_PackedUSD::getIntrinsicPurposes( UT_StringArray& purposes ) const
{
    purposes.clear();
    if( m_purposes & GUSD_PURPOSE_PROXY )
        purposes.append( UT_StringHolder( UT_StringHolder::REFERENCE, "proxy" ));
    if( m_purposes & GUSD_PURPOSE_RENDER )
        purposes.append( UT_StringHolder( UT_StringHolder::REFERENCE, "render" ));
    if( m_purposes & GUSD_PURPOSE_GUIDE )
        purposes.append( UT_StringHolder( UT_StringHolder::REFERENCE, "guide" ));
}