class_docstr: Combine function that computes metric using initial state from extracts.
code: def compact(self, accumulator: Any) -> Any:
      self._num_compacts.inc(1)
      return super().compact(accumulator)
  
imports: import copy
  import datetime
  import itertools
  import numbers
  from typing import Any, Dict, Iterable, Iterator, List, NamedTuple, Optional, Tuple, Type, TypeVar, Union
  import apache_beam
  import numpy
  from tensorflow_model_analysis import constants
  from tensorflow_model_analysis.api import types
  from tensorflow_model_analysis.evaluators import counter_util
  from tensorflow_model_analysis.evaluators import eval_saved_model_util
  from tensorflow_model_analysis.evaluators import evaluator
  from tensorflow_model_analysis.evaluators import jackknife
  from tensorflow_model_analysis.evaluators import keras_util
  from tensorflow_model_analysis.evaluators import metrics_validator
  from tensorflow_model_analysis.evaluators import poisson_bootstrap
  from tensorflow_model_analysis.extractors import slice_key_extractor
  from tensorflow_model_analysis.metrics import metric_specs
  from tensorflow_model_analysis.metrics import metric_types
  from tensorflow_model_analysis.metrics import metric_util
  from tensorflow_model_analysis.proto import config_pb2
  from tensorflow_model_analysis.slicer import slicer_lib
  from tensorflow_model_analysis.utils import model_util
  from tensorflow_model_analysis.utils import util
  from tensorflow_metadata.proto.v0 import schema_pb2
label_desc: Use image node_id 3 for calling the _ComputationsCombineFn obj's underlying member method code with example usage: obj.compact(accumulator) and returns: super