docs: def launch_eval_job(tag, m1_path, m2_path, job_name, completions):
      """Launches an evaluator job.
      tag: name for this eval job (used as top level folder name)
      m1_path, m2_path: full gs:// paths to the .pb files to match up
      job_name: string, appended to the container, used to differentiate the job
      names (e.g. 'minigo-cc-evaluator-v5-123-v7-456')
      completions: the number of completions desired (each completion is 2 games)
      """
      print()
      if not re.match(r'[a-z0-9-]*$', tag, re.I):
          print("{} is not a valid tag".format(tag))
          return
  
      # TODO: Change to minigo-pub
      sgf_bucket_path = "sethtroisi-sandbox/experiments/eval/" + tag
      assert not sgf_bucket_path.startswith("gs://"), bucket_pat
      bucket_path = "gs://" + sgf_bucket_path
  
  
      metadata_path = os.path.join(bucket_path, 'metadata')
      assert not gfile.Exists(metadata_path), "Already exists"
  
      TS=str(int(time.time()))
      metadata = {
          'timestamp': TS,
          'date': datetime.datetime.now().isoformat(' '),
          'model1': os.path.basename(m1_path),
          'model2': os.path.basename(m2_path),
          'model1_path': m1_path,
          'model2_path': m2_path,
          'job_name': job_name,
          'completions': completions,
          'launch_eval_version' : LAUNCH_EVAL_VERSION,
      }
  
      job_conf, resp_bw, resp_wb = launch_eval.launch_eval_job(
          m1_path, m2_path, job_name, sgf_bucket_path, completions)
  
      if not (resp_bw and resp_wb):
          print("launch_eval.py failed")
          print(job_conf)
          print(resp_bw)
          print(resp_wb)
          print()
          assert False
  
      # Jobs were launched, record metadata to GCS.
      with gfile.GFile(metadata_path, "w") as metadata_file:
          json.dump(metadata, metadata_file)
  
      with gfile.GFile(os.path.join(bucket_path, 'commands'), "w") as f:
          f.write(str(sys.argv) + "\n")
  
  
      with gfile.GFile(os.path.join(bucket_path, 'job_conf'), "w") as f:
          f.write(str(job_conf) + "\n")