anchor.diff:       test_jun_pandas_len_index,
        test_jun_pandas_memory_usage,
        test_jun_pandas_info_columns,
  -     test_jun_pandas_selection].
  +     test_jun_pandas_selection,
  +     test_jun_pandas_single_selection].
   
   init_per_testcase(_, _Config) ->
       % for each case start a new worker
  
positive.code:     test_jun_pandas_len_index/1,
      test_jun_pandas_memory_usage/1,
      test_jun_pandas_info_columns/1,
      test_jun_pandas_selection/1]).
  
  all() ->
      [test_jun_pandas_columns,
  
negative.code: -include_lib("eunit/include/eunit.hrl").
  
  -define(DATAFRAME, 'pandas.core.frame.DataFrame').
  -define(SERIES, 'pandas.core.frame.Series').
  
  -export([all/0, init_per_testcase/2, end_per_testcase/2]).
  -export([test_jun_pandas_columns/1,
  