code: def _test_masks(self):
      raise NotImplementedError()
  
file_path: h2o-3/h2o-py/h2o/cross_validation.py
imports: from h2o.utils.compatibility import *
label_desc: Use image node_id 3 for calling the H2OPartitionIterator obj's underlying member method code with example usage: obj._test_masks() without return types