class_docstr: Computes normalized discounted cumulative gain.
class_docstr_tok: ["Computes","normalized","discounted","cumulative","gain","."]
code: def create_accumulator(self):
      return _State(ndcg=self._new_ndcg_dict(), weight=0.0)
  
file_path: model-analysis/tensorflow_model_analysis/evaluators/query_metrics/ndcg.py
imports: from typing import Any, Dict, Iterable, List, NamedTuple, Tuple
  import apache_beam
  import numpy
  from tensorflow_model_analysis.evaluators.query_metrics import query_types
  from tensorflow_model_analysis.post_export_metrics import metric_keys
label_desc: Use image node_id 5 for calling the NdcgMetricCombineFn obj's underlying member method code with example usage: obj.create_accumulator() and returns: _State