code: def test_head():
      assert head((inc, 1)) == inc
      assert head((add, 1, 2)) == add
      assert head((add, (inc, 1), (inc, 1))) == add
      assert head([1, 2, 3]) == list
  
file_path: dask/dask/tests/test_rewrite.py
imports: from __future__ import annotations
  from dask.rewrite import VAR, RewriteRule, RuleSet, Traverser, args, head
  from dask.utils_test import add, inc
label_desc: Use image node_id 2 for calling a global function with example usage: test_head() without return types