sealed classes

[adsharma]

There is some discussion on typing-sig about sealed classes here:
https://mail.python.org/archives/list/typing-sig@python.org/thread/QSCT2N4RFPRQN2U7NIX6VCNVNDHGO22U/

Perhaps you can chime in with your thoughts as the author of this library.

@sealed
class Tree:
    EMPTY: None
    LEAF: Leaf
    NODE: Node
  
@dataclass  
class Leaf:
   data: int
   
@dataclass
class Node:
   left: Tree
   right: Tree  

would be nice. Other python libraries with similar functionality linked from here:

https://www.reddit.com/r/Python/comments/ipqqca/sum_types_discriminated_unions_for_python/

is pretty nice syntactically.