code: def first_leaf_of(node: LN) -> Optional[Leaf]:
      """Returns the first leaf of the node tree."""
      if isinstance(node, Leaf):
          return node
      if node.children:
          return first_leaf_of(node.children[0])
      else:
          return None
  
imports: import sys
  from typing import Final, Generic, Iterator, List, Optional, Set, Tuple, TypeVar, Union
  from mypy_extensions import mypyc_attr
  from black.cache import CACHE_DIR
  from black.mode import Mode, Preview
  from black.strings import get_string_prefix, has_triple_quotes
  from blib2to3 import pygram
  from blib2to3.pgen2 import token
  from blib2to3.pytree import NL, Leaf, Node, type_repr
label_desc: Use image node_id 9 for calling a global function with example usage: first_leaf_of(node) and returns: node, first_leaf_of, None