\cdbproperty{Traceless}{}

Indicates that the tensor is traceless:
  any internal index contraction makes the tensor vanish.
\begin{screen}{1,2,3}
A_{m n}::Traceless.
A_{m}^{m};
@canonicalise!(%);
0;
\end{screen}
~

\cdbseealgo{canonicalise}
