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/glm/pyunit_PUBDEV_6160_custom_metric.py
imports: import sys
  import h2o
  from tests import pyunit_utils
  from tests.pyunit_utils import CustomMaeFunc, CustomRmseFunc, CustomLoglossFunc, dataset_prostate, dataset_iris
  from h2o.estimators.glm import H2OGeneralizedLinearEstimator
label_desc: Use image node_id 6 for calling a global function with example usage: custom_rmse_mm() and returns: h2o