class_docstr: A stats generator meant to be used as a part of a composite generator.
  
  A constituent stats generator facilitates sharing logic between several stats
  generators. It is functionally identical to a beam.CombineFn, but it expects
  add_input to be called with instances of InputBatch.
docstr: A class method which returns an ID for instances of this stats generator.
  
  This method should take all the arguments to the __init__ method so that the
  result of ConstituentStatsGenerator.key(*init_args) is identical to
  ConstituentStatsGenerator(*init_args).key(). This allows a
  CompositeStatsGenerator to construct a specific constituent generator in its
  __init__, and then recover the corresonding output value in its
  extract_composite_output method.
  
  Returns:
    A unique ID for instances of this stats generator class.
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code: def key(cls) -> Hashable:
      """A class method which returns an ID for instances of this stats generator.
  
      This method should take all the arguments to the __init__ method so that the
      result of ConstituentStatsGenerator.key(*init_args) is identical to
      ConstituentStatsGenerator(*init_args).key(). This allows a
      CompositeStatsGenerator to construct a specific constituent generator in its
      __init__, and then recover the corresonding output value in its
      extract_composite_output method.
  
      Returns:
        A unique ID for instances of this stats generator class.
      """
  
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 2 for calling the ConstituentStatsGenerator obj's underlying member method code with example usage: obj.key(cls) without return types