code: def get_image_extension(mimetype: str) -> str | None:
      return _suffix_from_mime.get(mimetype)
  
file_path: sphinx/sphinx/util/images.py
imports: from __future__ import annotations
  import base64
  from os import path
  from typing import TYPE_CHECKING, NamedTuple, overload
  import imagesize
label_desc: Use image node_id 5 for calling a global function with example usage: get_image_extension(mimetype) and returns: _suffix_from_mime