SLAVE CONTACT SURFACE - NODE SET NAME/ID

Gents,

I have got some problems with getting name or id of the node set which is a base for the contact surface (ABAQUS STD 3D profile)

To check if my slave surface is for sure based on nodeset, I have used following command:

set slave_def [hm_getentityvalue groups $slave2delete slavedefinition 0]

where 'slave2delete' variable contain name of slave surface. The return value is 4 which means this surface is built using node set. How can I get this set name or id?

I have tried to do it in so many ways but as far without success.

Thanks in advance for your help.

Slawek