This can be any name the SP requires however usually it is 'Groupsgroups'
Format:
attrname-format:URI
Script:
groups*.name
Column
width
60%
Panel
borderColor
#9EBEE5
bgColor
#f0f0f0
borderWidth
1px
...
Section
border
true
Column
If I log onto my SAML test app I can check to see if all the groups of which my account is a member of, are returned in the Groups 'groups' attribute, by looking at the full SAML assertion...