* simplify_indexed() now raises/lowers dummy indices to canonicalize the index
variance. This allows some simplifications that weren't possible before,
like eps~a.b~c~d*X.a*X~b -> 0 and X.a~a-X~a.a -> 0.
* simplify_indexed() now raises/lowers dummy indices to canonicalize the index
variance. This allows some simplifications that weren't possible before,
like eps~a.b~c~d*X.a*X~b -> 0 and X.a~a-X~a.a -> 0.