I tried the example in the manual but rieman to ricci doesn't seem to work
from cdb.relativity.abstract import *
from cdb.core.manip import *
{a,b,c,d,e,f,g,m,n,p,q,r,s,t,u,v,w,a,b,c,d,e,f}::Indices(vector).
R_{m n p q}::RiemannTensor;
ex:= R^{a}_{b c a} - R^{a}_{b a c};
riemann_to_ricci(ex);
The code returns none