code: def _test_latest(self):
      columns = TDS.columns
      pipe = Pipeline(
          columns={c.name: c.latest for c in columns},
      )
  
      cal_slice = slice(20, 40)
      dates_to_test = self.calendar[cal_slice]
      result = self.engine.run_pipeline(
          pipe,
          dates_to_test[0],
          dates_to_test[-1],
      )
      for column in columns:
          with ignore_pandas_nan_categorical_warning():
              col_result = result[column.name].unstack()
  
          expected_col_result = self.expected_latest(column, cal_slice)
          assert_frame_equal(col_result, expected_col_result)
  
file_path: catalyst/tests/pipeline/test_column.py
imports: from contextlib2 import ExitStack
  from unittest import TestCase
  from pandas import date_range, DataFrame
  from pandas.util.testing import assert_frame_equal
  from catalyst.lib.labelarray import LabelArray
  from catalyst.pipeline import Pipeline
  from catalyst.pipeline.data.testing import TestingDataSet
  from catalyst.testing import chrange, temp_pipeline_engine
  from catalyst.utils.pandas_utils import ignore_pandas_nan_categorical_warning
label_desc: Use image node_id 4 for calling the LatestTestCase obj's underlying member method code with example usage: obj._test_latest() without return types