code: def test_metrics_show_rev_without_metrics(metrics_repo):
      assert api.metrics_show(rev="HEAD~2") == {}
  
imports: import json
  import os
  from textwrap import dedent
  from typing import Dict, List
  import pytest
  from dvc import api
label_desc: Use image node_id 17 for calling a global function with example usage: test_metrics_show_rev_without_metrics(metrics_repo) without return types