TikZ test

This method is reused.

TODO

• Automate the generation of TikZ diagrams.

• Add counter to TikZ diagrams.

Demo

Similarly, we can construct the second cohomology of Lie algebras for classifying central extensions. An exact sequence of Lie algebras

is call a central extension if \(\lie{a}\) is abelian and \([\lie{a},\lie{b}]=0\).