#!/usr/local/bin/cadabra2
{s,r,l,k,m,n}::Indices(vector);
{s,r,l,k,m,n}::Integer(0..d-1);
\Gamma_{#}::GammaMatrix(metric=\delta);
\delta_{m n}::KroneckerDelta;
def post_process(ex):
	sort_product(ex)
	eliminate_kronecker(ex)
	canonicalise(ex)
	collect_terms(ex)
    
ex:=\Gamma_{s r} \Gamma_{r l} \Gamma_{k m} \Gamma_{m s};
for i in range(3):
	join_gamma(_)
	distribute(_)
    
factor_in(_, $d$);
collect_factors(ex);
tst:= \Gamma_{k l} (12 - 18 d + 8 d**2 - d**3) + \delta_{k l} ( - 3 + 6 d - 4 d**2 + d**3) - @(ex);
distribute(_)
assert(tst==0)