How can I check if an ideal has a direct sum decomposition? [GAP]

Question

I need a function to check if a left ideal of a Group Algebra has a direct sum decomposition or not. So, I need a function that return true if the left ideal has a direct sum decomposition or false if the left ideal doesn't have a direct sum decomposition (so the left ideal is irreducible). Just a function that verify if a left ideal is irreducible can help too. Is there a function to do this?

I have already created a list N with all the left ideals of R. And I have created another list B, where the left ideals are not repeated. Now, I need to check if these ideals that are on list B are irreducible, so I thought about checking if they are a direct sum of other ideals.

LoadPackage("wedderga");
G:=SymmetricGroup(3);
F:=GF(5);
R:=GroupRing(F,G);
N:=[]; 
for x in R do 
    I:=LeftIdeal(R,[x]);
    Add(N,I);
od;
B:=[]; 
for i in [1..Length(N)] do
    if not (N[i] in B) then
        Add(B, N[i]);
    fi;
od;