code: def test_show_stdv(self):
      param = {"max_depth": 2, "eta": 1, "objective": "binary:logistic"}
      num_round = 2
      dtrain, _ = tm.load_agaricus(__file__)
      xgb.cv(
          param,
          dtrain,
          num_round,
          nfold=5,
          metrics={"error"},
          seed=0,
          show_stdv=False,
      )
  
imports: import json
  import os
  import tempfile
  import numpy
  import pytest
  import xgboost
  from xgboost import testing
  from xgboost.testing.updater import ResetStrategy
label_desc: Use image node_id 9 for calling the TestModels obj's underlying member method code with example usage: obj.test_show_stdv() without return types