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: lightning-flash/tests/core/serve/test_dag/test_rewrite.py
imports: import pytest
  from flash.core.serve.dag.rewrite import VAR, RewriteRule, RuleSet, Traverser, args, head
  from flash.core.utilities.imports import _TOPIC_SERVE_AVAILABLE
label_desc: Use image node_id 4 for calling a global function with example usage: test_head() without return types