class_docstr: A StatsGenerator which computes statistics using a combiner function.
  
  This class computes statistics using a combiner function. It emits partial
  states processing a batch of examples at a time, merges the partial states,
  and finally computes the statistics from the merged partial state at the end.
  
  This object mirrors a beam.CombineFn except for the add_input interface, which
  is expected to be defined by its sub-classes. Specifically, the generator
  must implement the following four methods:
  
  Initializes an accumulator to store the partial state and returns it.
      create_accumulator()
  
  Incorporates a batch of input examples (represented as an arrow RecordBatch)
  into the current accumulator and returns the updated accumulator.
      add_input(accumulator, input_record_batch)
  
  Merge the partial states in the accumulators and returns the accumulator
  containing the merged state.
      merge_accumulators(accumulators)
  
  Compute statistics from the partial state in the accumulator and
  return the result as a DatasetFeatureStatistics proto.
      extract_output(accumulator)
docstr: Merges several accumulators to a single accumulator value.
  
  Note: mutating any element in `accumulators` except for the first is not
  allowed. The first element may be modified and returned for efficiency.
  
  Args:
    accumulators: The accumulators to merge.
  
  Returns:
    The merged accumulator.
docstr_tok: ["Merges","several","accumulators","to","a","single","accumulator","value",".","Note",":","mutating","any","element","in","`","accumulators","`","except","for","the","first","is","not","allowed",".","The","first","element","may","be","modified","and","returned","for","efficiency",".","Args",":","accumulators",":","The","accumulators","to","merge",".","Returns",":","The","merged","accumulator","."]
code: def merge_accumulators(
      self, accumulators: Iterable[ACCTYPE]
  ) -> ACCTYPE:
      """Merges several accumulators to a single accumulator value.
  
      Note: mutating any element in `accumulators` except for the first is not
      allowed. The first element may be modified and returned for efficiency.
  
      Args:
        accumulators: The accumulators to merge.
  
      Returns:
        The merged accumulator.
      """
      raise NotImplementedError
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import abc
  from typing import Any, Dict, Generic, Hashable, Iterable, List, Optional, Text, TypeVar
  import apache_beam
  import pyarrow
  from tensorflow_data_validation import types
  from tensorflow_data_validation.statistics.generators import input_batch
  from tensorflow_metadata.proto.v0 import schema_pb2
  from tensorflow_metadata.proto.v0 import statistics_pb2
label_desc: Use image node_id 4 for calling the CombinerStatsGenerator obj's underlying member method code with example usage: obj.merge_accumulators(accumulators) without return types