code: def custom_rmse_mm():
      return h2o.upload_custom_metric(
          CustomRmseFunc, func_name="rmse", func_file="mm_rmse.py"
      )
  
file_path: h2o-3/h2o-py/tests/testdir_algos/gbm/pyunit_custom_metrics_pubdev_5088.py
imports: import sys
  import h2o
  from tests import pyunit_utils
  from tests.pyunit_utils import CustomMaeFunc, CustomRmseFunc, CustomLoglossFunc, assert_correct_custom_metric, regression_model, multinomial_model, binomial_model
  from h2o.estimators.gbm import H2OGradientBoostingEstimator
label_desc: Use image node_id 2 for calling a global function with example usage: custom_rmse_mm() and returns: h2o