SymmetrizeCovDs only symmetrizes covariant derivatives that have been flagged as symmetrizable. This can be done by giving the option SymCovDQ -> True to DefCovD (or DefMetric) when the covariant derivative is defined.
Symmetrized covariant derivatives can be entered as e.g. CD[a,b,c,...][expr], and are symmetric in all indices on the derivative.
With caching turned on, the first result takes longer to compute because it has to be written to the cache. Subsequent symmetrizations will be faster however.
SymmetrizeCovDs can be called automatically by setting $AutoSymmetrizeCovDs to True.
The implementation of symmetrizing derivatives is exponentially complex in the number of derivatives. SymmetrizeCovDs has an optimized algorithm in the case when there is no torsion. Whenever there is torsion, a slower algorithm is used.
EXAMPLES
Basic Examples 
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