code: def isheader(elem: Element) -> bool:
      return elem.tag in ["h1", "h2", "h3", "h4", "h5", "h6"]
  
file_path: markdown/markdown/extensions/attr_list.py
imports: from __future__ import annotations
  from typing import TYPE_CHECKING
  from .None import Extension
  from ..treeprocessors import Treeprocessor
  import re
label_desc: Use image node_id 6 for calling a global function with example usage: isheader(elem) and returns: unknown