code: def test_reversability_categorical(self):
      class F(Classifier):
          inputs = ()
          window_length = 0
          dtype = categorical_dtype
          missing_value = "<missing>"
  
      f = F()
      column_data = LabelArray(
          np.array(
              [
                  ["a", f.missing_value],
                  ["b", f.missing_value],
                  ["c", "d"],
              ],
          ),
          missing_value=f.missing_value,
      )
  
      assert_equal(
          f.postprocess(column_data.ravel()),
          pd.Categorical(
              ["a", f.missing_value, "b", f.missing_value, "c", "d"],
          ),
      )
  
      # only include the non-missing data
      pipeline_output = pd.Series(
          data=["a", "b", "c", "d"],
          index=pd.MultiIndex.from_arrays(
              [
                  [
                      pd.Timestamp("2014-01-01"),
                      pd.Timestamp("2014-01-02"),
                      pd.Timestamp("2014-01-03"),
                      pd.Timestamp("2014-01-03"),
                  ],
                  [0, 0, 0, 1],
              ]
          ),
          dtype="category",
      )
  
      assert_equal(
          f.to_workspace_value(pipeline_output, pd.Index([0, 1])),
          column_data,
      )
  
imports: from functools import reduce
  import operator
  import numpy
  import pandas
  from zipline.lib.labelarray import LabelArray
  from zipline.pipeline import Classifier
  from zipline.pipeline.data.testing import TestingDataSet
  from zipline.pipeline.expression import methods_to_ops
  from zipline.testing import parameter_space
  from zipline.testing.fixtures import ZiplineTestCase
  from zipline.testing.predicates import assert_equal
  from zipline.utils.numpy_utils import categorical_dtype, int64_dtype
  from .base import BaseUSEquityPipelineTestCase
label_desc: Use image node_id 1 for calling the TestPostProcessAndToWorkSpaceValue obj's underlying member method code with example usage: obj.test_reversability_categorical() without return types