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: Returns a compact representation of the accumulator.
  
  This is optionally called before an accumulator is sent across the wire. The
  base class is a no-op. This may be overwritten by the derived class.
  
  Args:
    accumulator: The accumulator to compact.
  
  Returns:
    The compacted accumulator. By default is an identity.
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code: def compact(self, accumulator: ACCTYPE) -> ACCTYPE:
      """Returns a compact representation of the accumulator.
  
      This is optionally called before an accumulator is sent across the wire. The
      base class is a no-op. This may be overwritten by the derived class.
  
      Args:
        accumulator: The accumulator to compact.
  
      Returns:
        The compacted accumulator. By default is an identity.
      """
      return accumulator
  
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 5 for calling the CombinerStatsGenerator obj's underlying member method code with example usage: obj.compact(accumulator) and returns: accumulator