I am trying to simplify the expression below in SymPy.
The I tensors have 8-fold symmetry: I[0,1,2,3]=I[0,3,2,1]=I[1,2,3,0]=I[1,0,3,2]=I[2,3,0,1]=I
I
I[0,1,2,3]=I[0,3,2,1]=I[1,2,3,0]=I[1,0,3,2]=I[2,3,0,1]=I