code: def is_vararg(leaf: Leaf, within: Set[NodeType]) -> bool:
      """Return True if `leaf` is a star or double star in a vararg or kwarg.
  
      If `within` includes VARARGS_PARENTS, this applies to function signatures.
      If `within` includes UNPACKING_PARENTS, it applies to right hand-side
      extended iterable unpacking (PEP 3132) and additional unpacking
      generalizations (PEP 448).
      """
      if leaf.type not in VARARGS_SPECIALS or not leaf.parent:
          return False
  
      p = leaf.parent
      if p.type == syms.star_expr:
          # Star expressions are also used as assignment targets in extended
          # iterable unpacking (PEP 3132).  See what its parent is instead.
          if not p.parent:
              return False
  
          p = p.parent
  
      return p.type in within
  
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 20 for calling a global function with example usage: is_vararg(leaf, within) and returns: unknown, False, False