https://en.wikipedia.org/wiki/Total_variation_distance_of_probability_measures
\[\delta(P,Q) \leq \sqrt{\frac{1}{2} \mathcal{D}_\text{KL}(P \parallel Q)}\]https://en.wikipedia.org/wiki/Total_variation_distance_of_probability_measures
\[\delta(P,Q) \leq \sqrt{\frac{1}{2} \mathcal{D}_\text{KL}(P \parallel Q)}\]