code: def test_db_file_reader(self):
      ws = workspace.C.Workspace()
      session = LocalSession(ws)
      db_path = self._make_temp_path()
  
      # Build a cache DB file.
      cached_reader = CachedReader(
          self._build_source_reader(ws, 100),
          db_path=db_path,
          db_type="LevelDB",
      )
      build_cache_step = cached_reader.build_cache_step()
      session.run(build_cache_step)
  
      # Read data from cache DB file.
      db_file_reader = DBFileReader(
          db_path=db_path,
          db_type="LevelDB",
      )
      data = self._read_all_data(ws, db_file_reader, session)
      self.assertEqual(sorted(data), list(range(100)))
  
      self._delete_path(db_path)
  
imports: from caffe2.python.dataio import CompositeReader, CompositeReaderBuilder, ReaderBuilder, ReaderWithDelay, ReaderWithLimit, ReaderWithTimeLimit
  from caffe2.python.dataset import Dataset
  from caffe2.python.db_file_reader import DBFileReader
  from caffe2.python.pipeline import pipe
  from caffe2.python.schema import Struct, NewRecord, FeedRecord
  from caffe2.python.session import LocalSession
  from caffe2.python.task import TaskGroup, final_output, WorkspaceType
  from caffe2.python.test_util import TestCase
  from caffe2.python.cached_reader import CachedReader
  from caffe2.python import core, workspace, schema
  from caffe2.python.net_builder import ops
  import numpy
  import numpy.testing
  import os
  import shutil
  import unittest
  import tempfile
label_desc: Use image node_id 8 for calling the TestDBFileReader obj's underlying member method code with example usage: obj.test_db_file_reader() without return types