code: def _var_sort_key(s: str):
      """Sorts variables in order of use by JAX, short names first and `_` last."""
      return (1000 if s == "_" else len(s), s)
  
imports: from collections.abc import Mapping, Sequence
  import dataclasses
  import itertools
  import logging
  import os
  import sys
  from typing import Any, Callable, NamedTuple, Optional
  from haiku._src import summarise
  import jax
  import jax.core
label_desc: Use image node_id 5 for calling a global function with example usage: _var_sort_key(s) and returns: unknown,  s