class_docstr: Computes normalized discounted cumulative gain.
class_docstr_tok: ["Computes","normalized","discounted","cumulative","gain","."]
code: def merge_accumulators(
      self, accumulators: Iterable[_State]
  ) -> _State:
      accumulators = iter(accumulators)
      result = next(accumulators)
      for accumulator in accumulators:
          result = self._add_states(result, accumulator)
      return result
  
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 8 for calling the NdcgMetricCombineFn obj's underlying member method code with example usage: obj.merge_accumulators(accumulators) and returns: result