class_docstr: Generates statistics for number unique and top-k item counts.
  
  Uses mergeable K-Minimum Values (KMV) and Misra-Gries sketches to estimate
  statistics.
class_docstr_tok: ["Generates","statistics","for","number","unique","and","top-k","item","counts",".","Uses","mergeable","K-Minimum","Values","(","KMV",")","and","Misra-Gries","sketches","to","estimate","statistics","."]
code: def merge_accumulators(
      self,
      accumulators: Iterable[
          Dict[tfdv_types.FeaturePath, _CombinedSketch]
      ],
  ) -> Dict[tfdv_types.FeaturePath, _CombinedSketch]:
      it = iter(accumulators)
      result = next(it)
      for accumulator in it:
          for feature_name, combined_sketch in accumulator.items():
              existing_sketch = result.get(feature_name, None)
              if existing_sketch is None:
                  result[feature_name] = combined_sketch
              else:
                  existing_sketch.merge(combined_sketch)
                  result[feature_name] = existing_sketch
      return result
  
imports: import collections
  from typing import Dict, Iterable, Optional, Text
  import apache_beam
  import numpy
  import pyarrow
  from tensorflow_data_validation import constants
  from tensorflow_data_validation import types
  from tensorflow_data_validation.arrow import arrow_util
  from tensorflow_data_validation.statistics.generators import stats_generator
  from tensorflow_data_validation.utils import schema_util
  from tensorflow_data_validation.utils import stats_util
  from tensorflow_data_validation.utils import top_k_uniques_stats_util
  from tensorflow_data_validation.utils.example_weight_map import ExampleWeightMap
  from tfx_bsl.arrow import array_util
  from tfx_bsl.sketches import KmvSketch
  from tfx_bsl.sketches import MisraGriesSketch
  from tensorflow_metadata.proto.v0 import schema_pb2
  from tensorflow_metadata.proto.v0 import statistics_pb2
label_desc: Use image node_id 6 for calling the TopKUniquesSketchStatsGenerator obj's underlying member method code with example usage: obj.merge_accumulators(accumulators) and returns: result