class_docstr: Approximately computes unique values on the PCollection.
code: def extract_output(
      self, accumulator: sketches.MisraGriesSketch
  ) -> np.ndarray:
      estimate = accumulator.Estimate()
      estimate.validate()
      result = np.dstack(list(reversed(estimate.flatten())))
      if not result.size:
          result = np.array(
              [
                  [
                      analyzers.get_empy_vocabulary_dummy_value(
                          self._input_dtype
                      )
                  ]
              ],
              dtype=object,
          )
      # TODO(b/282952880): Avoid converting to pylist when we can always rely on
      # top_k sorted inputs.
      if self._output_pylist:
          return result.tolist()
      return result
  
imports: from typing import Any, Collection, List, Optional, Tuple, Union, Iterable, Sequence
  import numpy
  import pyarrow
  import tensorflow
  from tensorflow_transform import analyzer_nodes
  from tensorflow_transform import analyzers
  from tensorflow_transform import common
  from tensorflow_transform import common_types
  from tensorflow_transform import nodes
  from tensorflow_transform import tf_utils
  from tfx_bsl import sketches
  from tfx_bsl.types import tfx_namedtuple
  from typing_extensions import Protocol
label_desc: Use image node_id 5 for calling the _VocabularyCombiner obj's underlying member method code with example usage: obj.extract_output(accumulator) and returns: result, result