Christoffel-symbols
Calculate Christoffel symbols (e.g Schwarzschild metric, FLRW metric, Perturbed FLRW metric)
$\Gamma^{\mu}_{\nu \beta} = g^{\mu \nu} = \Gamma_{\nu \alpha \beta} $
where
\Gamma_{\nu \alpha \beta} = \frac{1}{2} [ {\d_{x^{\beta}}g_{\mu \alpha}} + {\d_{x^{\alpha}}g_{\mu \beta}} - {\d_{x^{\mu}}g_{\alpha \beta}} ]