 Vgroup #   0 contains:
 tag =   720 ref =   2  <--- neither vdata nor vgroup 
 
 Vgroup #   1 contains:
 tag =   1962 ref =   4  <--- is a vdata 
 
 Vgroup #   2 contains:
 tag =   1965 ref =   5  <--- is a vgroup 
 tag =   106 ref =   6  <--- neither vdata nor vgroup 
 tag =   701 ref =   6  <--- neither vdata nor vgroup 
 tag =   720 ref =   2  <--- neither vdata nor vgroup 
 
 Vgroup #   3 contains:
 tag =   1965 ref =   5  <--- is a vgroup 
 tag =   1965 ref =   7  <--- is a vgroup 
 
 Vgroup #   4 contains:
 tag =   1962 ref =   10  <--- is a vdata 
 tag =   1962 ref =   11  <--- is a vdata 
 tag =   1962 ref =   12  <--- is a vdata 
 
