Checking in the new AST node types
#12693 got merged 🎉. It took a few rewrites essentially but I fell that the design of the new nodes will allow us to scale with reasonable maintance cost when adding new language specific nodes. The base class for new AST nodes (Token) to sublcass from allows one to implement nodes in an expressive manner by setting __slots__. The constructor of Token then sets the .args of Basic based on __slots__ this has the benefit that you need not write setters and getters using @property decorators (which quickly becomes tiresome when you have many classes).
Checking in the refactored PythonPrinter and changes to lambdify
Finally the challenging work of refactoring lambdify got merged into SymPy's master branch: #13046. We eventually decided to drop the contents of the old translations dictionaries but leave them be (in an empty state) in case users were modifying those in their code. Hopefully this approach doesn't break any code out there. Given how popular lambdify is among SymPy's users, it is a bit worrying that the test suite is not that extensive. I do remember a google engineer mentioning that the follow the "Beyonce principle": "I you liked it you should have put a test on it". Funny at is may be I hope I don't need to defend these changes with that arguement.