How to find 'is_a'/'part_of' relationship using GO::Termfinder

Hello All,

I'm using Perl's GO::Termfinder to find  parent/child nodes of a given 
 node. I wonder How I can extract the type of relationship,
like 'is_a', 'part_of' etc. relationship that connects two nodes? Is there 
any better way to do this in Bioperl?

Thanks in advance