code: def _run_tests(tests, fail_fast):
      globs = _test_globals()
      to_skip = os.getenv("UAT_SKIP", "").split(",")
      for name in tests:
          print(f"Running {name}:")
          if _skip_test(name, to_skip):
              print("  skipped (user requested)")
              continue
          if _test_passed(name):
              print("  skipped (already passed)")
              continue
          filename = os.path.join("tests", "uat", name + ".md")
          if testlib.front_matter_skip_test(filename):
              print("  skipped (doctest options)")
              continue
          with UATContext():
              failed, attempted = testlib.run_test_file(
                  filename,
                  globs=globs,
                  fail_fast=fail_fast,
              )
          if not failed:
              print(f"  {attempted} test(s) passed")
              _mark_test_passed(name)
          else:
              sys.exit(1)
  
imports: import fnmatch
  import os
  import re
  import sys
  import tempfile
  import guild
  from guild import _test
  from guild import config
  from guild import pip_util
  from guild import util
label_desc: Use image node_id 5 for calling a global function with example usage: _run_tests(tests, fail_fast) without return types