When I use 'canonicalise', I find following code won't give right results

```
{\mu,\nu,\rho,\sigma}::Indices(vector).
A^{\mu\nu}::Symmetric.
B^{\mu\nu}::AntiSymmetric.
\tr{#}::LaTeXForm("{\rm Tr}").
\tr{#}::Trace.
\epsilon^{\mu\nu\rho\sigma}::EpsilonTensor.
{A^{\mu\nu}, B^{\mu\nu}}::ImplicitIndex.
ex1:=\epsilon^{\mu\nu\rho\sigma}\tr{A^{\mu\nu} B^{\rho\sigma}};
canonicalise(_);
ex2:=\epsilon^{\mu\nu\rho\sigma} \tr{A^{\mu\nu} B^{\rho\sigma}}+\epsilon^{\mu\nu\rho\sigma} \tr{A^{\nu\mu} B^{\rho\sigma}};
canonicalise(_);
ex3:=\tr{A^{\mu\nu}}\tr{B^{\mu\nu}};
canonicalise(_);
```