code: def test_letters_and_numbers(self):
      sorted_df = pd.DataFrame(
          columns=[
              "1",
              "2",
              "3",
              "a",
              "b",
              "c",
              "d",
          ]
      )
      shuffled_df = pd.DataFrame(
          columns=["c", "a", "1", "d", "3", "2", "b"]
      )
  
      assert_frame_equal(sort_df_by_columns(shuffled_df), sorted_df)
  
imports: import unittest
  import numpy
  import pandas
  from pandas.testing import assert_frame_equal
  from neptune.common.utils import align_channels_on_x, as_list, get_channel_name_stems, map_keys, map_values, merge_dataframes
  from tests.unit.neptune.legacy.random_utils import sort_df_by_columns
label_desc: Use image node_id 1 for calling the TestSortDfByColumns obj's underlying member method code with example usage: obj.test_letters_and_numbers() without return types