Identification of master and slave entities of a contact pair

I want to find the master and slave entities of a given contact pair. Assume that the master/slave entity is an element based group (element set).

The below API is what I used but its not giving any output.

hm_getvalue groups name=contactpair_name dataname=masterentityids

Kindly let me know, why this command is not giving the output and also if there is any other way for the above mention requirement.