code: def test_groupby_level_no_obs(self):
      # #1697
      midx = MultiIndex.from_tuples(
          [
              ("f1", "s1"),
              ("f1", "s2"),
              ("f2", "s1"),
              ("f2", "s2"),
              ("f3", "s1"),
              ("f3", "s2"),
          ]
      )
      df = DataFrame(
          [[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12]], columns=midx
      )
      df1 = df.loc(axis=1)[
          df.columns.map(lambda u: u[0] in ["f2", "f3"])
      ]
  
      msg = "DataFrame.groupby with axis=1 is deprecated"
      with tm.assert_produces_warning(FutureWarning, match=msg):
          grouped = df1.groupby(axis=1, level=0)
      result = grouped.sum()
      assert (result.columns == ["f2", "f3"]).all()
  
imports: import datetime
  import numpy
  import pytest
  import pandas
  from pandas import DataFrame, MultiIndex, Series
  import pandas._testing
label_desc: Use image node_id 6 for calling the TestMultiLevel obj's underlying member method code with example usage: obj.test_groupby_level_no_obs() without return types