code: def tearDown(self):
      shutil.rmtree(self.root_dir)
  
imports: import random
  import shutil
  import tempfile
  import pandas
  from nose.tools import assert_equals
  from catalyst.exchange.exchange_bcolz import BcolzExchangeBarWriter, BcolzExchangeBarReader
  from catalyst.exchange.exchange_bundle import ExchangeBundle
  from catalyst.exchange.utils.bundle_utils import get_df_from_arrays
label_desc: Use image node_id 3 for calling the TestBcolzWriter obj's underlying member method code with example usage: obj.tearDown() without return types