Missing 'getGroupMembers()'

Hi,

I'm trying to write a method such that my own classes can be used with the 
groups like "Summary" and "Math", but when I tried to look for examples or 
just wanted to get an idea of which functions are the members of a group, I 
found out that the function "getGroupMembers" is not present... I couldn't 
find an alternative function, if there is one. Does anyone know a solution?

Anton